～歳
～さい · ～sai · JLPT N5 · noun
old
🎂 sai sounds like sigh: one more birthday, one more sigh
Attach さい to a number to give an age: 五歳 (go-sai) = five years old. The kanji 歳 contains 止 (stop) and 戌, and originally meant a harvest year — each year that passes adds one 歳. Often written with the simpler 才 as shorthand.