An aircraft is a machine that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. The human activity that surrounds aircraft is called aviation. Crewed aircraft are flown by an onboard pilot, but unmanned aerial vehicles may be remotely controlled or self-controlled by onboard computers. Aircraft may be classified by different criteria, such as lift type, aircraft propulsion, usage and others.

An airline is a company that provides a regular service of air transportion for passengers or freight (cargo). Airlines use aircraft to supply these services. Many passenger airlines also carry cargo in the belly of their aircraft, while dedicated cargo airlines focus solely on freight transport. Generally, airline companies are recognized with an air operating certificate or license issued by a governmental aviation body. Airlines may be scheduled or charter operators. 

An airport is an aerodrome with extended facilities, mostly for commercial air transport. Airports usually consist of a landing area, which comprises an aerially accessible open space including at least one operationally active surface such as a runway for a plane to take off and to land or a helipad

Algae (UK: /ˈælɡiː/ AL-ghee, US: /ˈældʒiː/ ⓘ AL-jee; sg.: alga /ˈælɡə/ ⓘ AL-gə) is an informal term for any organisms of a large and diverse group of photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular microalgae, such as cyanobacteria[a], Chlorella, and diatoms, to multicellular macroalgae such as kelp or brown algae which may grow up to 50 metres (160 ft) in length. Most algae are aquatic organisms and lack many of the distinct cell and tissue types, such as stomata, xylem, and phloem that are found in land plants. The largest and most complex marine algae are called seaweeds. In contrast, the most complex freshwater forms are the Charophyta, a division of green algae which includes, for example, Spirogyra and stoneworts. Algae that are carried passively by water are plankton, specifically phytoplankton.

An altar is a table or platform for the presentation of religious offerings, for sacrifices, or for other ritualistic purposes. Altars are found at shrines, temples, churches, and other places of worship. They are used particularly in paganism, Christianity, Buddhism, Hinduism, Judaism, modern paganism, and in certain Islamic communities around Caucasia and Asia Minor. Many historical-medieval faiths also made use of them, including the Roman, Greek, and Norse religions.

American football (referred to simply as football in the United States and Canada), also known as gridiron football, is a team sport played by two teams of eleven players on a rectangular field with goalposts at each end.

Amphibians are ectothermic, anamniotic, four-limbed vertebrate animals that constitute the class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all tetrapods, excluding the amniotes (tetrapods with an amniotic membrane, such as modern reptiles, birds, and mammals). All extant (living) amphibians belong to the monophyletic subclass Lissamphibia, with three living orders: Anura (frogs), Urodela (salamanders), and Gymnophiona (caecilians). Evolved to be mostly semiaquatic, amphibians have adapted to inhabit a wide variety of habitats, with most species living in freshwater, wetland or terrestrial ecosystems (such as riparian woodland, fossorial and even arboreal habitats). Their life cycle typically starts out as aquatic larvae with gills known as tadpoles, but some species have developed behavioural adaptations to bypass this.

An amusement park is a park that features various attractions, such as rides and games, as well as other events for entertainment purposes. A theme park is a type of amusement park that bases its structures and attractions around a central theme, often featuring multiple areas with different themes. Unlike temporary and mobile funfairs and carnivals, amusement parks are stationary and built for long-lasting operation. They are more elaborate than city parks and playgrounds, usually providing attractions that cater to a variety of age groups. While amusement parks often contain themed areas, theme parks place a heavier focus with more intricately-designed themes that revolve around a particular subject or group of subjects.

Ancient art refers to the many types of art produced by the advanced cultures of ancient societies with different forms of writing, such as those of China, India, Mesopotamia, Persia, Egypt, Greece, and Rome. The art of pre-literate societies is normally referred to as prehistoric art and is not covered by the scope of the ancient era. Furthermore, although some pre-Columbian cultures developed writing in the centuries preceding the European discovery of the Americas, these advancements are, on grounds of dating, largely covered with the dedicated topic of pre-Columbian art and associated sub-topics, such as Maya art, Aztec art, and Olmec art. 

In Abrahamic religious traditions (such as Judaism, Christianity, and Islam) and some sects of other belief-systems like Hinduism and Buddhism, an angel is a heavenly supernatural or spiritual being. In monotheistic belief-systems, such beings are under service of the supreme deity (i.e. God).

Abrahamic religions often depict angels as benevolent celestial intermediaries between God and humanity. Other roles include protectors and guides for humans, such as guardian angels and servants of God.[3] Abrahamic religions describe angelic hierarchies, which vary by religion and sect. Some angels have specific names (such as Gabriel or Michael) or titles (such as seraph or archangel). Malevolent angels are often believed to have been expelled from Heaven and called fallen angels. In many such religions, the Devil (or devils) are identified with such angels

Angling (from Old English angol, meaning "hook") is a fishing technique that uses a fish hook attached to a fishing line to tether individual fish in the mouth. The fishing line is usually manipulated with a fishing rod, although rodless techniques such as handlining also exist. Modern angling rods are usually fitted with a fishing reel that functions as a cranking device for storing, retrieving and releasing out the line, although Tenkara fishing and traditional cane pole fishing are two rod-angling methods that do not use any reel. The fish hook itself can be additionally weighted with a denser tackle called a sinker, and is typically dressed with an appetizing bait (i.e. hookbait) to attract and entice the fish into swallowing the hook, but sometimes an inedible fake/imitation bait with multiple attached hooks (known as a lure) is used instead of a single hook with edible bait. Some type of bite indicator, such as a float, a bell or a quiver tip, is often used to relay underwater status of the hook to the surface and alert the angler of a fish's presence. 

Animals are multicellular, eukaryotic organisms of the kingdom Animalia (also called Metazoa). All animals are motile, meaning they can move spontaneously and independently, at some point in their lives. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their lives. All animals are heterotrophs: they must ingest other organisms or their products for sustenance.

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. For example, the first event is the initial occurrence or, if planned, the inaugural of the event. One year later would be the first anniversary 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. The important dates in a sitting monarch's reign may also be commemorated, an event often referred to as a "Jubilee".

Antarctica  is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. Antarctica is the fifth-largest continent, being about 40% larger than Europe, and has an area of 14,200,000 km2 (5,500,000 sq mi). Most of Antarctica is covered by the Antarctic ice sheet, with an average thickness of 1.9 km (1.2 mi).

Anteaters are the four extant mammal species in the suborder Vermilingua (meaning "worm tongue"), commonly known for eating ants and termites. The individual species have other names in English and other languages. Together with sloths, they are within the order Pilosa. The name "anteater" is also commonly applied to the aardvark, numbat, echidnas, and pangolins, although they are not closely related to them.

The term antelope refers to numerous extant or recently extinct species of the ruminant artiodactyl family Bovidae that are indigenous to most of Africa, India, the Middle East, Central Asia, and a small area of Eastern Europe. Antelopes do not form a monophyletic group, as some antelopes are more closely related to other bovid groups, like bovines, goats, and sheep, than to other antelopes.

A better definition, also known as the "true antelopes", includes only the genera Gazella, Nanger, Eudorcas, and Antilope. One North American mammal, the pronghorn or "pronghorn antelope", is colloquially referred to as the "American antelope", despite the fact that it belongs to a completely different family (Antilocapridae) than the true Old-World antelopes; pronghorn are the sole extant member of an extinct prehistoric lineage that once included many unique species. 

Anthropology is the scientific study of humanity, concerned with human behavior, human biology, cultures, societies, and linguistics, in both the present and past, including past human species. Social anthropology studies patterns of behavior, while cultural anthropology studies cultural meaning, including norms and values. A portmanteau term sociocultural anthropology is commonly used today. Linguistic anthropology studies how language influences social life. Biological or physical anthropology studies the biological development of humans

Anti-racism encompasses a range of ideas and political actions which are meant to counter racial prejudice, systemic racism, and the oppression of specific racial groups. Anti-racism is usually structured around conscious efforts and deliberate actions which are intended to create equal opportunities for all people on both an individual and a systemic level. As a philosophy, it can be engaged in by the acknowledgment of personal privileges, confronting acts as well as systems of racial discrimination and/or working to change personal racial biases. Major contemporary anti-racism efforts include the Black Lives Matter (BLM) movement and workplace anti-racism