aril |
a second or outer covering of some seeds. |

arioso |
in the manner of an aria or song (used as a musical direction). [3 definitions] |

arise |
to come into view or existence; emerge. [4 definitions] |

arista |
a bristlelike appendage on the spikelets of certain grains and grasses; awn. [2 definitions] |

aristocracy |
a high-ranking social class, having special privileges and influence and usu. determined by heredity. [5 definitions] |

aristocrat |
a member of a titled or privileged class. [3 definitions] |

aristocratic |
of or concerning aristocrats or government by aristocrats. [2 definitions] |

Aristotelian |
of, concerning, or derived from Aristotle or his philosophy. [3 definitions] |

Aristotle |
a Greek philosopher (384-322 B.C.). |

arithmetic |
the simplest form of mathematics consisting of the theory and computation of whole numbers, including addition, subtraction, multiplication, division, evolution, and involution. [3 definitions] |

arithmetician |
one skilled in arithmetic. |

arithmetic mean |
the sum of a series of quantities divided by the number of quantities; average. |

arithmetic progression |
a sequence of numbers that results from adding a constant number, such as 4, to each previous number, and thus obtaining a series such as 6, 10, 14, 18, 22, 26. |

-arium |
a place or device associated with or pertaining to; -orium. |

Arius |
a Greek theologian and Christian priest in Alexandria (256?-336 A.D.). |

Arizona |
a southwestern U.S. state between California and New Mexico. (abbr.: AZ) |

ark |
(sometimes cap.) according to the Old Testament, a large boat built by Noah to preserve life during the Flood. [4 definitions] |

Arkansas |
a south central U.S. state between Mississippi and Oklahoma. (abbr.: AR) |

ark of the covenant |
according to the Old Testament, the sacred chest in which the ancient Hebrews carried the two stone tablets inscribed with the Ten Commandments. |

arm^{1} |
either of the two upper limbs of the human body, between the shoulders and the wrists. [3 definitions] |

arm^{2} |
(usu. pl.) weapons, esp. those that shoot or explode. [7 definitions] |