| 22nd Amendment |
an amendment to the U.S. Constitution that ensures that no person can be elected to more than two four-year terms as President of the United States. The 22nd Amendment, ratified in 1951, was passed in reaction to President Franklin D. Roosevelt's four terms in office. |
| abscess |
a sore that forms within the tissues of the body and is filled with pus. Abscesses can be caused by an infection. |
| absolute temperature |
temperature measured on a scale in which zero equals the lowest temperature that can be obtained physically. |
| account |
an arrangement wherein a bank or other financial institution holds a customer's deposited funds so that the funds are safe but can be accessed at any time by the customer, or the conception of this arrangement as a container for the funds that are kept. [1/16 definitions] |
| ace |
a serve in tennis that wins a point because the other player can not reach the ball. [1/5 definitions] |
| acid |
a substance that has a sour taste and, if it is very strong, can sometimes burn a hole in something that it touches. |
| acrobat |
a person who can do physical acts that take balance and skill. |
| actinic rays |
electromagnetic radiation, such as x-rays or ultraviolet light, that can produce an image on a photographic emulsion. |
| activation code |
a set of characters, consisting of numbers, letters, characters, or a combination of these, that is sent by a website to a user's email so that the website can verify the user's email address and comply with the user's request to begin a new service or change personal information. Once received, the user enters the code into the provided box on the website so that fulfillment of the user's request can begin. |
| addition table |
a table that can be used to find the sum of two numbers. |
| address |
to write information on, telling where something can be delivered. [1/6 definitions] |
| adenoid |
(usually plural) a mass of tissue that grows behind the nose in the upper part of the throat. When swollen, the adenoids can make breathing difficult. |
| aflatoxin |
any of a group of toxic compounds produced by certain molds, esp. those in the genus Aspergillus. Consumption of food contaminated with these molds can cause liver disease and cancer. |
| agitator |
a machine, or part of a machine, that automatically shakes or stirs things together, as in a can of paint or a washing machine. [1/2 definitions] |
| aircraft |
any machine that can fly through the air. |
| aircraft carrier |
a very large ship with a flat deck on which airplanes can take off and land. |
| air lock |
an airtight compartment in which the air pressure can be regulated, usu. situated between two areas that have different air pressures, as in underwater operations. [1/2 definitions] |
| airplane |
a machine that is heavier than air and that can fly. It has wings and engines. |
| air pocket |
a downward air current that can cause an abrupt change, usu. a drop, in an aircraft's altitude. |
| airport |
a large area of level land where airplanes can land and take off. |
| air shaft |
a narrow vertical passage through which fresh air can reach an otherwise enclosed area such as the interior of a building; ventilating shaft. |