1Throughout the year; all year round.
この地域は年中暖かい気候だ。
This region is warm throughout the year.
年中無休で営業しています。
We are open year-round without holidays.
果物は年中手に入るわけではない。
Fruits are not available all year round.
2Always; all the time; continually (used adverbially, often to emphasize how frequently something happens).
彼は年中忙しそうにしている。
He seems busy all the time.
年中体調が悪いと言っている友人がいる。
I have a friend who says they're unwell all the time.
年中行列ができる人気店だ。
It's a popular shop that has lines all year round.
3During an era or a particular year of an era (used in historical/literary contexts).
年中に起きた事件について記録が残っている。
There are records about incidents that occurred during that year/era.
4A kindergarten class level (nenchū) — the middle year in preschool, between the younger and older classes.
うちの子は来年、年中に上がる予定だ。
My child will move up to the second year of kindergarten next year.
年中組は年少組よりも活動が活発になる。
The nenchū class becomes more active than the nen-shō class.