period of an apprentice's contract (usu. ten years)
apprenticeship; indentureship; indenture
one-year period
彼の年季は十年だった。
His apprenticeship period was ten years.
職人の道具には年季が入っていた。
The craftsman's tools were seasoned by long use.
昔の日本では、多くの若者が年季奉公で技術を学んだ。
In old Japan, many young people learned skills through apprenticeship.