歳 means “age, years old, year”

さい · sai

Also: year-end, occasion, opportunity

Kun'yomi (Japanese reading)
とし, とせ, よわい
On'yomi (Chinese reading)
サイ, セイ

JLPT N3 · Taught in secondary school · 13 strokes

The story

Picture a harvest blade (戈) laid down (止) once a year: 歳 counts years, of crops and of people. 三歳 is three years old, 二十歳 has a reading all its own, はたち, and 万歳, "ten thousand years", is the cheer banzai.

Used in 三歳 (sansai, three years old), 二十歳 (hatachi, twenty years old), and 万歳 (banzai, hurrah)

More from Life & Breath

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Readings from KANJIDIC2, © EDRDG, CC BY-SA.