cardinal definition

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; denotes a quantity but not the order
3. a variable color averaging a vivid red
4. crested thick-billed North American finch having bright red plumage in the male
5. serving as an essential component
• examples: a cardinal rule
• examples: the central cause of the problem
• examples: an example that was fundamental to the argument
• examples: computers are fundamental to modern industrial structure
6. being or denoting a numerical quantity but not order
• examples: cardinal numbers