中【ちゅう / じゅう】

中 after a noun has two readings with two meanings. Read ちゅう, it means "in the middle of": an activity is under way, or something happens during it. Read じゅう, it means "all through": the whole of a place or of a stretch of time.

ちゅう: in the middle of

After a noun for an activity – a meeting, a class, a meal, roadworks – ちゅう says it is going on. Shop signs use it: えいぎょうちゅう営業中 "open", じゅんびちゅう準備中 "not open yet". With に it marks something that happens during the activity.

じゅう: all through

After a place, じゅう covers all of it: せかいじゅう世界中, にっぽんちゅう日本中, かちゅう家中, たいちゅう体中. After a stretch of time, it covers the whole of it: いちにち一日ちゅう中 "all day", いちねん一年ちゅう中 "all year".

By the end of

With に after きょう今日, こんしゅう今週 or ことし今年, 中 means "before it is over". 今日中 and 今年中 are read じゅう; 今週中 and 今月中 are heard with either reading. ごぜんちゅう午前中, "in the morning", is always ちゅう.

• × 一日中に終わらせた → 一日で終わらせた