אַחַת לְ...

ביטוי (אנגלית)

Once every…

הגדרה (אנגלית)

Once in..., once every certain period of time; rarely.

("The remainder of the incense — once every sixty or seventy years they would prepare it in halves; therefore, an individual who prepared it in halves was liable, said Rabban Shimon ben Gamliel in the name of the deputy high priest, but as for a third or a quarter, I have not heard" – Keritot 6b)