The counter 1才 is used for counting: 1 year old (age) (Category: 才/歳 (sai) - Age, JLPT N5). 一 (ichi) contracts with 才 (sai) to form 'issai' (double consonant sokuon sound change).
Context Example
子供が1才になりました。
Kodomo ga issai ni narimashita.
My child turned one year old.
Which counter represents "1 year old (age)"?
Correct! 🎉
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