Main entry: cardinal
Definition: being or denoting a numerical quantity but not order
Usage: cardinal numbers
Antonyms: ordinal
Definition: being or denoting a numerical order in a series
Main entry: cardinal, central, key, primal, fundamental
Definition: serving as an essential component
Usage: a cardinal rule; the central cause of the problem; an example that was fundamental to the argument; computers are fundamental to modern industrial structure
Antonyms: unimportant
Definition: not important