(baseball) Second base, because it is often the key to scoring and defense.

plural of keystone

(ecology) A species that exerts a large, stabilizing influence throughout an ecological community, despite its relatively small numerical abundance.

plural of keyspace

(cryptography) The notional space that contains all possible cryptographic keys. / (databases) A NoSQL object that includes column families.

(computing, telegraphy) An input device whose few keys can be pressed in many combinations, often simultaneously, to enter different commands or characters.

plural of keyset

(business, marketing) A pricing method where the price is doubled at each level of distribution.

(cryptography) A stream of random or pseudorandom characters that are combined with the plaintext to produce a ciphertext.

plural of keystream