noun. A key; specifically, a key to or an aid to the understanding of something difficult, as a cipher, or the study of a foreign or classic author in his own language.

noun. A key; a glossary.

noun. A Roman key.

noun. A device for restraint of the hands.

noun. A glossary.

noun. A key; an identification guide; a series of logically organized groups of discriminating information which aims to allow the user to correctly identify a taxon.

"After his election Gregory X set out some hard-line regulations for future elections: his 1274 constitution Ubi periculum contains the first use of the word conclave—from the Latin cum clavis, “with a key.”"

glossary  key