1. (all) through (e.g. the night); throughout (e.g. the year); all ... long
春休み中ずっとアルバイトをしていた。I worked part-time all through spring break.
2. within (e.g. the week); in the course of (e.g. today); by the end of
as 〜に
明日中にお金がいるんだ。I need the money by tomorrow.
3. all over; throughout (e.g. the world)
大陸中で有名な物語よ。It is a story famous throughout the continent.
4. all (of a group); the whole (family, school, etc.)
クラス中が笑いに包まれた。The whole class was enveloped in laughter.