| algae |
organisms that live mainly in the water and make their food through photosynthesis. Algae are different from plants in that they have no true leaves, roots, or stems. Seaweeds are algae. "Algae" is a plural noun; the singular form is "alga." |
| alien |
a living being from another planet; extraterrestrial. There is no evidence that aliens exist, but many people believe there is life on other planets. [2/5 definitions] |
| alimentary canal |
the tube in the body through which food travels as it is digested. The alimentary canal goes from the mouth to the anus, and includes the esophagus, the stomach, and the small and large intestines. |
| all along |
from the beginning; the whole time. |
| alone |
apart from everyone or everything else. [1/3 definitions] |
| Alps |
a high mountain range that goes from southern France through Switzerland, Italy, Germany, and Austria and into the countries along the Adriatic Sea down to Albania. |
| already |
from an earlier time. [1/3 definitions] |
| alternate |
different from the usual; substitute. [1/7 definitions] |
| Amazon |
the longest river in South America. It flows from the Andes mountains in Peru across northern Brazil to the Atlantic Ocean. [1/2 definitions] |
| Amazon River |
a major river of South America that flows from the Andes Mountains in Peru across northern Brazil to the Atlantic Ocean. |
| amber |
a hard, yellow or brown material that is used to make jewelry. It is a fossil that comes from the resin of pine trees. [1/2 definitions] |
| ambush |
a surprise attack made from a hidden place. [3 definitions] |
| American Revolution |
the war of 1775-83 in which the American colonies won their independence from Great Britain. |
| ammonia |
the liquid made from mixing ammonia gas with water. Certain cleaners are made with ammonia. [1/2 definitions] |
| ammunition |
the objects fired from any weapon, or material that can be exploded. Bullets, bombs, and gunpowder are types of ammunition. [1/2 definitions] |
| amphitheater |
an oval or round building with seats rising in rows from an open, central area. Amphitheaters are used for sports and other public events. |
| -an |
a suffix that means "from," "belongs to," or "lives in." [1/2 definitions] |
| ancestor |
a person from whom one is descended and who lived several generations ago. |
| anchor |
a heavy object that is dropped from a boat or ship by a cable to keep the vessel from moving. [1/4 definitions] |
| angle1 |
the figure made by two lines coming from a single point. [1/4 definitions] |
| Angora |
(often lower case) yarn or cloth made from either of these kinds of hair. Angora is used to make sweaters and other articles of clothing. [1/3 definitions] |