Key Pair

Two mathematically related keys having the properties that
1) one key can be used to encrypt a message that can only be decrypted using the other key, and
2) even knowing one key, it is computationally infeasible to discover the other key.
SOURCE: SP 800-32

A public key and its corresponding private key; a key pair is used with a public key algorithm.
SOURCE: SP 800-21; CNSSI-4009