Satellite (biology)

A satellite is a subviral agent that depends on the coinfection of a host cell with a helper virus for its replication. 　Satellites can be divided into two major classes: satellite viruses and satellite nucleic acids. 　Satellite viruses, which are most commonly associated with plants, are also found in mammals, arthropods, and bacteria. 　They encode structural proteins to enclose their genetic material, which are therefore distinct from the structural proteins of their helper viruses. 　Satellite nucleic acids, in contrast, do not encode their own structural proteins, but instead are encapsulated by proteins encoded by their helper viruses. 　The genomes of satellites range upward from 359 nucleotides in length for satellite tobacco ringspot virus RNA (STobRV). 　Most viruses have the capability to use host enzymes or their own replication machinery to independently replicate their own viral RNA. 　Satellites, in contrast, are completely dependent on a helper virus for replication. 　The symbiotic relationship between a satellite and a helper virus to catalyze the replication of a satellite genome is also dependent on the host to provide components like replicases to carry out replication. 　A satellite virus of mamavirus that inhibits the replication of its host has been termed a virophage. 　However, the usage of this term remains controversial due to the lack of fundamental differences between virophages and classical satellite viruses.

Heaven

Heaven, or the heavens, is a common religious cosmological or transcendent supernatural place where beings such as deities, angels, souls, saints, or venerated ancestors are said to originate, be enthroned, or reside. 　According to the beliefs of some religions, heavenly beings can descend to Earth or incarnate and earthly beings can ascend to Heaven in the afterlife or, in exceptional cases, enter Heaven alive. 　Heaven is often described as a "highest place", the holiest place, a Paradise, in contrast to hell or the Underworld or the "low places" and universally or conditionally accessible by earthly beings according to various standards of divinity, goodness, piety, faith, or other virtues or right beliefs or simply divine will. 　Some believe in the possibility of a heaven on Earth in a world to come. 　Another belief is in an axis mundi or world tree which connects the heavens, the terrestrial world, and the underworld. 　In Indian religions, heaven is considered as Svarga loka, and the soul is again subjected to rebirth in different living forms according to its karma. 　This cycle can be broken after a soul achieves Moksha or Nirvana. 　Any place of existence, either of humans, souls or deities, outside the tangible world (Heaven, Hell, or other) is referred to as the otherworld. 　At least in the Abrahamic faiths of Christianity, Islam, and some schools of Judaism, as well as Zoroastrianism, heaven is the realm of Afterlife where good actions in the previous life are rewarded for eternity (hell being the place where bad behavior is punished).

Stairs

Stairs are a structure designed to bridge a large vertical distance between lower and higher levels by dividing it into smaller vertical distances. 　This is achieved as a diagonal series of horizontal platforms called steps which enable passage to the other level by stepping from one to another step in turn. 　Steps are very typically rectangular. 　Stairs may be straight, round, or may consist of two or more straight pieces connected at angles. 　Types of stairs include staircases (also called stairways), ladders, and escalators. 　Some alternatives to stairs are elevators (also called lifts), stairlifts, inclined moving walkways, and ramps. 　A stairwell is a vertical shaft or opening that contains a staircase. 　A flight (of stairs) is an inclined part of a staircase consisting of steps (and their lateral supports if supports are separate from steps).

Dating

Dating is a stage of romantic relationships in which two individuals engage in an activity together, most often with the intention of evaluating each other's suitability as a partner in a future intimate relationship. 　It falls into the category of courtship, consisting of social events carried out by the couple either alone or with others. 　The protocols and practices of dating and the terms used to describe it vary vastly between cultures, societies, and time periods. 　Although dating is most often colloquially used to refer to the action of individuals engaging in dates with one other, dating can also encompass a wide range of activities which fall outside participation in social events. 　The meaning of dating also shifted during the 20th century to include a more informal use referring to a romantic, sexual relationship itself beyond an introductory or trial stage. 　Although informal, this meaning is very common and is used in formal speech as well as writing. 　Although taboo across most of the world for much of history, premarital sex has become increasingly common within the last century, beginning with the onset of the sexual revolution. 　Across a greater number of portrayals in film, television, and music, sex within dating has become increasingly accepted as a natural progression of the relationship.

Arizona

Arizona (/ˌærɪˈzoʊnə/ (listen) ARR-ih-ZOH-nə; Navajo: Hoozdo Hahoodzo [hoː˥z̥to˩ ha˩hoː˩tso˩]; O'odham: Alĭ ṣonak [ˈaɭi̥ ˈʂɔnak]) is a state in the Southwestern United States. 　It is the 6th-largest and the 14th-most-populous of the 50 states. 　Its capital and largest city is Phoenix. 　Arizona is part of the Four Corners region with Utah to the north, Colorado to the northeast, and New Mexico to the east; its other neighboring states are Nevada to the northwest, California to the west and the Mexican states of Sonora and Baja California to the south and southwest. 　Arizona is the 48th state and last of the contiguous states to be admitted to the Union, achieving statehood on February 14, 1912. 　Historically part of the territory of Alta California in New Spain, it became part of independent Mexico in 1821. 　After being defeated in the Mexican–American War, Mexico ceded much of this territory to the United States in 1848. 　The southernmost portion of the state was acquired in 1853 through the Gadsden Purchase. 　Southern Arizona is known for its desert climate, with very hot summers and mild winters. 　Northern Arizona features forests of pine, Douglas fir, and spruce trees; the Colorado Plateau; mountain ranges (such as the San Francisco Mountains); as well as large, deep canyons, with much more moderate summer temperatures and significant winter snowfalls. 　There are ski resorts in the areas of Flagstaff, Alpine, and Tucson. 　In addition to the internationally known Grand Canyon National Park, which is one of the world's seven natural wonders, there are several national forests, national parks, and national monuments. 　Arizona's population and economy have grown dramatically since the 1950s because of inward migration, and the state is now a major hub of the Sun Belt. 　Cities such as Phoenix and Tucson have developed large, sprawling suburban areas. 　Many large companies, such as PetSmart and Circle K, have headquarters in the state, and Arizona is home to major universities, including the University of Arizona and Arizona State University. 　Traditionally, the state is politically known for national conservative figures such as Barry Goldwater and John McCain, though it voted Democratic in the 1996 presidential race and in the 2020 presidential and senatorial elections. 　Arizona is home to a diverse population. 　About one-quarter of the state is made up of Indian reservations that serve as the home of 27 federally recognized Native American tribes, including the Navajo Nation, the largest in the state and the United States, with more than 300,000 citizens. 　Since the 1980s, the proportion of Hispanics in the state's population has grown significantly owing to migration from Mexico. 　In terms of religion, a substantial portion of the population are followers of the Roman Catholic Church and the Church of Jesus Christ of Latter-day Saints (LDS Church).

Weapon

A weapon, arm or armament is any implement or device that can be used to deter, threaten, inflict physical damage, harm, or kill. 　Weapons are used to increase the efficacy and efficiency of activities such as hunting, crime, law enforcement, self-defense, warfare, or suicide. 　In broader context, weapons may be construed to include anything used to gain a tactical, strategic, material or mental advantage over an adversary or enemy target. 　While ordinary objects – sticks, rocks, bottles, chairs, vehicles – can be used as weapons, many objects are expressly designed for the purpose; these range from simple implements such as clubs, axes and swords, to complicated modern firearms, tanks, intercontinental ballistic missiles, biological weapons, and cyberweapons. 　Something that has been re-purposed, converted, or enhanced to become a weapon of war is termed weaponized, such as a weaponized virus or weaponized laser.

Weapon (biology)

In biology, weapons are traits that are used by males to fight one another off for access to mates. 　A mate is won in battle either by a male chasing off a fellow competitor or killing it off, usually leaving the victor as the only option for the female to reproduce with. 　However, because stronger organisms, whether mentally or physically, are usually favored in combat, this also leads to the evolution of stronger organisms in species that use combat as a way to secure mates, via intrasexual selection. 　Examples of weapons include: antlers, horns, and ossicones.

Tennessee

Tennessee (/ˌtɛnɪˈsiː/ (listen) TEN-ih-SEE, locally /ˈtɛnɪsi/ TEN-iss-ee), officially the State of Tennessee, is a landlocked state in the Southeastern region of the United States. 　Tennessee is the 36th-largest by area and the 15th-most populous of the 50 states. 　It is bordered by Kentucky to the north, Virginia to the northeast, North Carolina to the east, Georgia, Alabama, and Mississippi to the south, Arkansas to the southwest, and Missouri to the northwest. 　Tennessee is geographically, culturally, and legally divided into three Grand Divisions of East, Middle, and West Tennessee. 　Nashville is the state's capital and largest city, and anchors its largest metropolitan area. 　Other major cities include Memphis, Knoxville, Chattanooga, and Clarksville. 　Tennessee's population as of the 2020 United States census is approximately 6.9 million. 　Tennessee is rooted in the Watauga Association, a 1772 frontier pact generally regarded as the first constitutional government west of the Appalachian Mountains. 　Its name derives from "Tanasi", a Cherokee town in the eastern part of the state that existed before the first European American settlement. 　Tennessee was initially part of North Carolina, and later the Southwest Territory, before its admission to the Union as the 16th state on June 1, 1796. 　It earned the nickname "The Volunteer State" early in its history due to a strong tradition of military service. 　A slave state until the American Civil War, Tennessee was politically divided, with its western and middle parts supporting the Confederacy and the eastern region harboring pro-Union sentiment. 　As a result, Tennessee was the last state to secede and the first readmitted to the Union after the war. 　During the 20th century, Tennessee transitioned from a predominantly agrarian society to a more diversified economy. 　This was aided in part by massive federal investment in the Tennessee Valley Authority (TVA) and the city of Oak Ridge, which was established during World War II to house the Manhattan Project's uranium enrichment facilities for the construction of the world's first atomic bombs. 　After the war, the Oak Ridge National Laboratory became a key center of scientific research. 　In 2016, the element tennessine was named for the state, largely in recognition of the roles played by Oak Ridge, Vanderbilt University, and the University of Tennessee in its discovery. 　Tennessee has also played a major role in the development of many forms of popular music, including country, blues, rock and roll, soul, and gospel. 　Tennessee has diverse terrain and landforms, and from east to west, contains a mix of cultural features characteristic of Appalachia, the Upland South, and the Deep South. 　The Blue Ridge Mountains along the eastern border reach some of the highest elevations in eastern North America, and the Cumberland Plateau contains many scenic valleys and waterfalls. 　The central part of the state is marked by cavernous bedrock and irregular rolling hills, and level, fertile plains define West Tennessee. 　The state is twice bisected by the Tennessee River, and the Mississippi River forms its western border. 　Its economy is dominated by the health care, music, finance, automotive, chemical, electronics, and tourism sectors, and cattle, soybeans, corn, poultry, and cotton are its primary agricultural products. 　The Great Smoky Mountains National Park, the nation's most visited national park, is in eastern Tennessee.

Beta

Beta (UK: /ˈbiːtə/, US: /ˈbeɪtə/; uppercase Β, lowercase β, or cursive ϐ; Ancient Greek: βῆτα, romanized: bē̂ta or Greek: βήτα, romanized: víta) is the second letter of the Greek alphabet. 　In the system of Greek numerals, it has a value of 2. 　In Ancient Greek, beta represented the voiced bilabial plosive IPA: [b]. 　In Modern Greek, it represents the voiced labiodental fricative IPA: [v] while IPA: [b] in borrowed words is instead commonly transcribed as μπ. 　Letters that arose from beta include the Roman letter ⟨B⟩ and the Cyrillic letters ⟨Б⟩ and ⟨В⟩.

Legislation

Legislation is the process or result of enrolling, enacting, or promulgating laws by a legislature, parliament, or analogous governing body. 　Before an item of legislation becomes law it may be known as a bill, and may be broadly referred to as "legislation" while it remains under consideration to distinguish it from other business. 　Legislation can have many purposes: to regulate, to authorize, to outlaw, to provide (funds), to sanction, to grant, to declare, or to restrict. 　It may be contrasted with a non-legislative act by an executive or administrative body under the authority of a legislative act.

Anthony

Anthony or Antony is a masculine given name, derived from the Antonii, a gens (Roman family name) to which Mark Antony (Marcus Antonius) belonged. 　According to Plutarch, the Antonii gens were Heracleidae, being descendants of Anton, a son of Heracles. 　Anthony is an English name that is in use in many countries. 　It has been among the top 100 most popular male baby names in the United States since the late 19th century and has been among the top 100 male baby names between 1998 and 2018 in many countries including Canada, Australia, England, Ireland and Scotland. 　Equivalents include Antonio in Italian, Spanish, Portuguese and Maltese; Αντώνιος in Greek; António or Antônio in Portuguese; Antoni in Catalan, Polish, and Slovene; Anton in Dutch, Galician, German, Icelandic, Romanian, Russian, and Scandinavian languages; Antoine in French; Antal in Hungarian; and Antun or Ante in Croatian. 　The usual abbreviated form is Tony (sometimes "Tone", "Ant", "Anth" or "Anton"). 　Its use as a Christian name was due to the veneration of St. Anthony the Great, the founder of Christian monasticism, particularly in Egypt. 　Also significant was the later cult of St. Anthony of Padua. 　In the United States, it is the 43rd most popular male name as of 2021, according to the Social Security Administration. 　When the background is Italian, Nino or Toni, shortened from Antonino, are used. 　Its popularity in the United Kingdom peaked during the 1940s; in 1944 it was the sixth most popular male name and was still as high as 14th in 1964.

Crystal

A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. 　In addition, macroscopic single crystals are usually identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations. 　The scientific study of crystals and crystal formation is known as crystallography. 　The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification. 　The word crystal derives from the Ancient Greek word κρύσταλλος (krustallos), meaning both "ice" and "rock crystal", from κρύος (kruos), "icy cold, frost". 　Examples of large crystals include snowflakes, diamonds, and table salt. 　Most inorganic solids are not crystals but polycrystals, i.e. many microscopic crystals fused together into a single solid. 　Polycrystals include most metals, rocks, ceramics, and ice. 　A third category of solids is amorphous solids, where the atoms have no periodic structure whatsoever. 　Examples of amorphous solids include glass, wax, and many plastics. 　Despite the name, lead crystal, crystal glass, and related products are not crystals, but rather types of glass, i.e. amorphous solids. 　Crystals, or crystalline solids, are often used in pseudoscientific practices such as crystal therapy, and, along with gemstones, are sometimes associated with spellwork in Wiccan beliefs and related religious movements.

Definition

A definition is a statement of the meaning of a term (a word, phrase, or other set of symbols). 　Definitions can be classified into two large categories: intensional definitions (which try to give the sense of a term), and extensional definitions (which try to list the objects that a term describes). 　Another important category of definitions is the class of ostensive definitions, which convey the meaning of a term by pointing out examples. 　A term may have many different senses and multiple meanings, and thus require multiple definitions. 　In mathematics, a definition is used to give a precise meaning to a new term, by describing a condition which unambiguously qualifies what a mathematical term is and is not. 　Definitions and axioms form the basis on which all of modern mathematics is to be constructed.

Tool

A tool is an object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. 　Although many animals use simple tools, only human beings, whose use of stone tools dates back hundreds of millennia, have been observed using tools to make other tools. 　Early human tools, made of such materials as stone, bone, and wood, were used for preparation of food, hunting, manufacture of weapons, and working of materials to produce clothing and useful artifacts. 　The development of metalworking made additional types of tools possible. 　Harnessing energy sources, such as animal power, wind, or steam, allowed increasingly complex tools to produce an even larger range of items, with the Industrial Revolution marking an inflection point in the use of tools. 　The introduction of widespread automation in the 19th and 20th centuries allowed tools to operate with minimal human supervision, further increasing the productivity of human labor. 　By extension, concepts which support systematic or investigative thought are often referred to as "tools" or as "toolkits".

Anniversary

An anniversary is the date on which an event took place or an institution was founded in a previous year, and may also refer to the commemoration or celebration of that event. 　The word was first used for Catholic feasts to commemorate saints. 　Most countries celebrate national anniversaries, typically called national days. 　These could be the date of independence of the nation or the adoption of a new constitution or form of government. 　There is no definite method for determining the date of establishment of an institution, and it is generally decided within the institution by convention. 　The important dates in a sitting monarch's reign may also be commemorated, an event often referred to as a "jubilee".

Pink

Pink is the color of a namesake flower that is a pale tint of red. 　It was first used as a color name in the late 17th century. 　According to surveys in Europe and the United States, pink is the color most often associated with charm, politeness, sensitivity, tenderness, sweetness, childhood, femininity, and romance. 　A combination of pink and white is associated with chastity and innocence, whereas a combination of pink and black links to eroticism and seduction. 　In the 21st century, pink is seen as a symbol of femininity, though this has not always been true; in the 1920s, pink was seen as a color that reflected masculinity.

Sudden

James Green aka "Sudden" is a fictional character created by an English author Oliver Strange in the early 1930s as the hero of a series, originally published by George Newnes Books Ltd, set in the American Wild West era. 　Oliver Strange died in 1952, and the series was revived by Frederick H. Christian in the 1960s. 　Christian classified the books as "Piccadilly westerns", that is books written by English authors, simply drawing on the conventions the genre, with no first hand experience of America. 　The Sudden books are among the earliest and best-loved of the type. 　Sudden is portrayed as an intrepid and accurate gunfighter in search of two men who cheated his foster father. 　James Green earns the nickname "Sudden" because of his lightning speed with a gun. 　Sudden is portrayed as a stereotypical gunfighter: an intelligent and resourceful drifting cowboy who is respectful of the law, unwilling to use a gun unless absolutely necessary, humanitarian, brave, strong, and fair. 　The first book was published in 1930 and was followed by 10 more until the 1940s and featured vivid descriptions of the western American landscape, rare in an author at that time. 　The series became popular for its exciting narrations combining elements of mystery, suspense, and action, with engaging characters, in a Wild West setting of dusty towns, ranches, and saloons.

Downtown

Downtown is a term primarily used in North America by English speakers to refer to a city's sometimes commercial, cultural and often the historical, political and geographic heart. 　It is often synonymous with its central business district (CBD). 　Downtowns typically contain a small percentage of a city’s employment. 　In some metropolitan areas it is marked by a cluster of tall buildings, cultural institutions and the convergence of rail transit and bus lines. 　In British English, the term "city centre" is most often used instead.

Simulation

A simulation is the imitation of the operation of a real-world process or system over time. 　Simulations require the use of models; the model represents the key characteristics or behaviors of the selected system or process, whereas the simulation represents the evolution of the model over time. 　Often, computers are used to execute the simulation. 　Simulation is used in many contexts, such as simulation of technology for performance tuning or optimizing, safety engineering, testing, training, education, and video games. 　Simulation is also used with scientific modelling of natural systems or human systems to gain insight into their functioning, as in economics. 　Simulation can be used to show the eventual real effects of alternative conditions and courses of action. 　Simulation is also used when the real system cannot be engaged, because it may not be accessible, or it may be dangerous or unacceptable to engage, or it is being designed but not yet built, or it may simply not exist. 　Key issues in modeling and simulation include the acquisition of valid sources of information about the relevant selection of key characteristics and behaviors used to build the model, the use of simplifying approximations and assumptions within the model, and fidelity and validity of the simulation outcomes. 　Procedures and protocols for model verification and validation are an ongoing field of academic study, refinement, research and development in simulations technology or practice, particularly in the work of computer simulation.

Correlation

In statistics, correlation or dependence is any statistical relationship, whether causal or not, between two random variables or bivariate data. 　Although in the broadest sense, "correlation" may indicate any type of association, in statistics it usually refers to the degree to which a pair of variables are linearly related. 　Familiar examples of dependent phenomena include the correlation between the height of parents and their offspring, and the correlation between the price of a good and the quantity the consumers are willing to purchase, as it is depicted in the so-called demand curve. 　Correlations are useful because they can indicate a predictive relationship that can be exploited in practice. 　For example, an electrical utility may produce less power on a mild day based on the correlation between electricity demand and weather. 　In this example, there is a causal relationship, because extreme weather causes people to use more electricity for heating or cooling. 　However, in general, the presence of a correlation is not sufficient to infer the presence of a causal relationship (i.e., correlation does not imply causation). 　Formally, random variables are dependent if they do not satisfy a mathematical property of probabilistic independence. 　In informal parlance, correlation is synonymous with dependence. 　However, when used in a technical sense, correlation refers to any of several specific types of mathematical operations between the tested variables and their respective expected values. 　Essentially, correlation is the measure of how two or more variables are related to one another. 　There are several correlation coefficients, often denoted ρ {\displaystyle \rho } or r {\displaystyle r} , measuring the degree of correlation. 　The most common of these is the Pearson correlation coefficient, which is sensitive only to a linear relationship between two variables (which may be present even when one variable is a nonlinear function of the other). 　Other correlation coefficients – such as Spearman's rank correlation – have been developed to be more robust than Pearson's, that is, more sensitive to nonlinear relationships. 　Mutual information can also be applied to measure dependence between two variables.

Commissioner

A commissioner (commonly abbreviated as Comm'r) is, in principle, a member of a commission or an individual who has been given a commission (official charge or authority to do something). 　In practice, the title of commissioner has evolved to include a variety of senior officials, often sitting on a specific commission. 　In particular, the commissioner frequently refers to senior police or government officials. 　A high commissioner is equivalent to an ambassador, originally between the United Kingdom and the Dominions and now between all Commonwealth states, whether Commonwealth realms, republics or countries having a monarch other than that of the realms. 　The title is sometimes given to senior officials in the private sector; for instance, many North American sports leagues. 　There is some confusion between commissioners and commissaries because other European languages use the same word for both. 　Therefore titles such as commissaire in French, Kommissar in German and comisario in Spanish or commissario in Italian, can mean either commissioner or commissary in English, depending on the context.

Bedroom

A bedroom or bedchamber is a room situated within a residential or accommodation unit characterised by its usage for sleeping and sexual activity. 　A typical western bedroom contains as bedroom furniture one or two beds (ranging from a crib for an infant, a single or twin bed for a toddler, child, teenager, or single adult to bigger sizes like a full, double, queen, king or California king [eastern or waterbed size for a couple]), a clothes closet, and bedside table and dressing table, both of which usually contain drawers. 　Except in bungalows, ranch style homes, ground floor apartments, or one-storey motels, bedrooms are usually on one of the floors of a dwelling that is above ground level.

Howard

Howard is an English-language given name originating from Old French Huard (or Houard) from a Germanic source similar to Old High German *Hugihard "heart-brave", or *Hoh-ward, literally "high defender; chief guardian". 　It is also probably in some cases a confusion with the Old Norse cognate Haward (Hávarðr), which means "high guard" and as a surname also with the unrelated Hayward. 　In some rare cases it is from the Old English eowu hierde "ewe herd". 　In Anglo-Norman the French digram -ou- was often rendered as -ow- such as tour → tower, flour (western variant form of fleur) → flower, etc. (with svarabakhti). 　A diminutive is "Howie" and its shortened form is "Ward" (most common in the 19th century). 　Between 1900 and 1960, Howard ranked in the U.S. Top 200; between 1960 and 1990, it ranked in the U.S. Top 400; between 1990 and 2004, it ranked in the U.S. Top 600. 　People with the given name Howard or its variants include:

Concrete

Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. 　Concrete is the second-most-used substance in the world after water, and is the most widely used building material. 　Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminum combined.　[citation needed] Globally, the ready-mix concrete industry, the largest segment of the concrete market, is projected to exceed $600 billion in revenue by 2025. 　This widespread use results in a number of environmental impacts. 　Most notably, the production process for cement produces large volumes of greenhouse gas emissions, leading to net 8% of global emissions. 　Other environmental concerns include widespread illegal sand mining, impacts on the surrounding environment such as increased surface runoff or urban heat island effect, and potential public health implications from toxic ingredients. 　Significant research and development is being done to try to reduce the emissions or make concrete a source of carbon sequestration, and increase recycled and secondary raw materials content into the mix to achieve a circular economy. 　Concrete is expected to be a key material for structures resilient to climate disasters, as well as a solution to mitigate the pollution of other industries, capturing wastes such as coal fly ash or bauxite tailings and residue. 　When aggregate is mixed with dry Portland cement and water, the mixture forms a fluid slurry that is easily poured and molded into shape. 　The cement reacts with the water through a process called concrete hydration that hardens over several hours to form a hard matrix that binds the materials together into a durable stone-like material that has many uses. 　This time allows concrete to not only be cast in forms, but also to have a variety of tooled processes preformed. 　The hydration process is exothermic, which means ambient temperature plays a significant role in how long it takes concrete to set. 　Often, additives (such as pozzolans or superplasticizers) are included in the mixture to improve the physical properties of the wet mix, delay or accelerate the curing time, or otherwise change the finished material. 　Most concrete is poured with reinforcing materials (such as rebar) embedded to provide tensile strength, yielding reinforced concrete. 　In the past, lime based cement binders, such as lime putty, were often used but sometimes with other hydraulic cements, (water resistant) such as a calcium aluminate cement or with Portland cement to form Portland cement concrete (named for its visual resemblance to Portland stone). 　Many other non-cementitious types of concrete exist with other methods of binding aggregate together, including asphalt concrete with a bitumen binder, which is frequently used for road surfaces, and polymer concretes that use polymers as a binder. 　Concrete is distinct from mortar. 　Whereas concrete is itself a building material, mortar is a bonding agent that typically holds bricks, tiles and other masonry units together.