Grammar detail: 中（ちゅう, じゅう)

中（ちゅう, じゅう) - throughout; while; out of; during etc.

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中 is a versatile character that can be used in several ways.

On its own, it is typically read なか, and means 'inside'. For example:

へや

部屋

の

なか

中

inside the room

However, it is commonly appended to other nouns, and used to convey the idea of 'throughout' or 'all over'. In this form, it is typically read じゅう. For example:

いちねんじゅう
一年中
throughout the year, all year round
いちにちじゅう
一日中
all day long, throughout the day
へやじゅう
部屋中
all over the room, throughout the room

When added to durations, it can also be used to convey the idea of duration, and is typically read as ちゅう, sometimes as じゅう (and in rare cases, either, with slightly different meanings). For example:

いちじかんちゅう
一時間中
for one hour
いちにちちゅう
1 日中
for one day

中 can also be used to indicate that something is in progress. In this situation, it is usually read as ちゅう.

りょこうちゅう
旅行中
on a trip
じゅんびちゅう
準備中
preparations underway

中 can be used to illustrate a part of a whole. For example:

ろくにん
6 人
ちゅう
中

ごにん
5 人
の
いしゃ
医者
five out of six doctors

More information / references

Advanced: more information on when to use ちゅう or じゅう ⇗