1. Of foremost importance; paramount: a cardinal rule; cardinal sins.
2. Dark to deep or vivid red.

1. (Abbr. Card.) Roman Catholic Church. A high church official, ranking just below the pope, who has been appointed by a pope to membership in the College of Cardinals.
2. A dark to deep or vivid red.
3. A North American finch (Cardinalis cardinalis) having a crested head, a short thick bill, and bright red plumage in the male.
4. A short hooded cloak, originally of scarlet cloth, worn by women in the 18th century.
5. A cardinal number.

[Middle English, from Late Latin cardinālis, principal, pivotal, from Latin, serving as a hinge, from cardō, cardin-, hinge.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.