一いっ歳さい

い

っ

さ

い

Meanings

1

one-year-old

Used for a person or animal that is one year old. Often appears in phrases like 一歳の誕生日 (first birthday) or 一歳児 (one-year-old child).

Our child will soon be one year old.

一いっ歳さいの誕たん生じょう日びにケーキを用よう意いした。

We prepared a cake for the first birthday.

〈人ひと〉が一いっ歳さいになるto turn one year old
息子むすこはもうすぐ一いっ歳さいになる。
My son will turn one year old soon.
〈人ひと〉と一いっ歳さい違ちがいa one-year age difference from someone
妹いもうととは一いっ歳さい違ちがいだ。
My little sister and I are one year apart in age.

一ひとつ
一つ is the general counter for one thing, while 一歳 specifically counts age in years.
一いっ歳さい児じ
一歳児 is a compound meaning 'one-year-old child', using 一歳 as a modifier.

一いっ歳さい
Standard kanji spelling for age; 歳 is the usual character for years of age.
一いっ才さい
Simplified variant using 才 instead of 歳; common in informal contexts or when writing for children.
１いっ歳さい
Arabic numeral spelling; common in forms, tables, and casual writing.
１いっ才さい
Arabic numeral with simplified 才; seen in informal contexts.

Compound of 一 (one) and 歳 (year of age). The reading いっさい results from the combination of いち and さい with gemination.