Definition of cardinal:
(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
the number of elements in a mathematical set; denotes a quantity but not the order
a variable color averaging a vivid red
crested thick-billed North American finch having bright red plumage in the male
serving as an essential component; "a cardinal rule"; "the central cause of the problem"; "an example that was fundamental to the argument"; "computers are fundamental to modern industrial structure"
being or denoting a numerical quantity but not order; "cardinal numbers"