Translation guide
Expressing a duration of one year or a single year in time.
Expressing a period of one year.
Standard way to say 'for one year' as a duration. The suffix 〜間 emphasizes the span of time.
日本に一年間住んでいました。
I lived in Japan for one year.
I'm planning a one-year study abroad.
Can mean 'one year' as a duration, but without 〜間 it may sound more like a point in time or a general count. Often used in compounds or when the duration is clear from context.
Without 〜間, it can be ambiguous; 一年間 is clearer for duration.
一年待ちました。
I waited one year.
Referring to one specific year, such as a calendar year or a year of age.
Used for 'one year' as a unit, like a calendar year or a year in school.
一年は三百六十五日です。
One year is 365 days.
彼は一年生です。
He is a first-year student.
Describing someone or something that is one year old.
Standard counter for age. Note the irregular reading いっさい.
娘は一歳になりました。
My daughter turned one year old.
Can be used for animals or inanimate objects, but 一歳 is standard for people.
Expressing frequency of once per year.
Standard pattern for 'once a year'. 一年に + frequency.
一年に一回健康診断を受けます。
I get a health checkup once a year.
More formal/literary alternative. 年 (ねん) means 'year' and 一度 (いちど) means 'once'.
年に一度の祭りが開かれます。
A festival is held once a year.
日本に一年間います。
I will be in Japan for one year.
彼女は一歳です。
She is one year old.
This dog is one year old.