一期一会 (Ichi-go ichi-e)

Literally: One time one meeting

Example: “旅先の出会いは一期一会だから大切にしたい。” — Meetings on a trip are once in a lifetime, so I want to cherish them.

English equivalent: Once in a lifetime

Origin: Associated with Sen no Rikyū, the 16th-century tea master who shaped much of the philosophy behind the Japanese tea ceremony during the late Sengoku and Azuchi-Momoyama periods — though Rikyū himself left no writings of his own, and the phrase survives only because his student Yamanoue Sōji recorded it as his teacher's own words in the Yamanoue Sōji Ki. "Ichi-go," a Buddhist term for a single lifetime, combined with "ichi-e," a single meeting, together frame every tea gathering as a completely unrepeatable event: even between the same host and guests, that exact moment, that exact mood, and that exact shared attention will never occur again in precisely the same way, so both sides owe each other complete sincerity while it lasts.