Kleis is the ordinary Greek word for a key -- the instrument that locks and unlocks a door. In the New Testament, however, every occurrence is figurative: the 'keys of the kingdom' entrusted to Peter (Matt 16:19), the 'key of knowledge' hoarded by the lawyers (Luke 11:52), and the keys of Death and Hades held by the risen Christ (Rev 1:18). The image is strikingly consistent: a key represents delegated authority over a domain. Spanish llave, French clef, and German Schluessel all translate it uniformly, confirming that the metaphor of authoritative access is the single operative sense in the NT.