adj. 1.serving as an essential component 2.being or denoting a numerical quantity but not order cardinal n. 1.(Roman Catholic Church) one of a group of more than 100 prominent bishops in the Sacred College who advise the Pope and elect new Popes 2.the number of elements in a mathematical set 3.a variable color averaging a vivid red 4.crested thick-billed North American finch having bright red plumage in the male
