テスト中（ちゅう）に私（わたし）の携帯（けいたい）が鳴（な）ってしまった。

食事（しょくじ）中（ちゅう）にスマホをいじるのはやめなさい。

一日（いちにち）中（じゅう）、勉強（べんきょう）をした。

授業（じゅぎょう）中（ちゅう）に、トイレに行（い）きたくなった。

まだ考（かんが）え中（ちゅう）だから、決（き）めていないよ。

あの同僚（どうりょう）は仕事（しごと）中（ちゅう）なのにいつも彼女（かのじょ）とメールをする不真面目（ふまじめ）な奴（やつ）だ。

僕（ぼく）はダイエット中（ちゅう）なのに、ケーキがあったら食（た）べてしまう。

今晩（こんばん）中（じゅう）にこの仕事（しごと）を終（お）わらせないといけないから、今夜（こんや）は徹夜（てつや）だ。

ポケモンは、日本（にほん）中（じゅう）だけでなく、世界（せかい）中（じゅう）で流行（はや）ったゲームだ。

何度（なんど）かけても電話（でんわ）中（ちゅう）だ。誰（だれ）と長（なが）電話（でんわ）しているんだろう…

試合（しあい）中（ちゅう）に足（あし）を怪我（けが）してしまって、松葉杖（まつばづえ）がなければ歩（ある）けない。

今年（ことし）中（じゅう）にこのプロジェクトを完成（かんせい）させなかったら、他社（たしゃ）に遅（おく）れをとってしまう。

What is the difference between 〜ている and 〜中?

How do we decide if 中 is ちゅう or じゅう?

<div class='writeup-body'>As a suffix, 中（ちゅう） is frequently used to highlight a period of time (or space). By attaching the case marking particle に, the sentence can be modified, to show that (B) is happening/existing throughout the timeframe/space of (A). This is often translated as 'throughout (A), (B)', or 'during (A), (B)'. First, let's take a look at 中（ちゅう） being used to show events that are in process.<ul class='writeup-examples--holder'><li class='writeup-example'><div class='writeup-example--japanese'>今（いま）は仕事（しごと）中（ちゅう）なんだ。</div><div class='writeup-example--english'> I am in the middle of working right now.</div></li><li class='writeup-example'><div class='writeup-example--japanese'>締（し）め切（き）りは今月（こんげつ）中（ちゅう）なんです。</div><div class='writeup-example--english'>The deadline is sometime (during) this month.</div></li></ul>Now, to show that a (B) event is happening within (A), simply add the case marking particle に to show a 'temporal location'. This will be done by attaching に to the end of any noun that you would like to indicate as the being the 'space' within which another thing exists/occurs.<ul class='writeup-examples--holder'><li class='writeup-example'><div class='writeup-example--japanese'>彼（かれ）は休憩（きゅうけい）中（ちゅう）に本（ほん）を読（よ）む。</div><div class='writeup-example--english'>He reads books during his break. (At some point during the act of taking a break)</div></li><li class='writeup-example'><div class='writeup-example--japanese'>私（わたし）は勉強（べんきょう）中（ちゅう）に話（はな）されるのが嫌（きら）いだ。</div><div class='writeup-example--english'>I don't like being talked to while studying. (At some point during the act of study)</div></li><li class='writeup-example'><div class='writeup-example--japanese'> 今日（きょう）中（じゅう）にレポートを提出（ていしゅつ）してください。</div><div class='writeup-example--english'>Please submit your papers by today. (Within today as the limit)</div></li><li class='writeup-example'><div class='writeup-example--japanese'>今年（ことし）中（じゅう）にイタリアに行（い）きたい。</div><div class='writeup-example--english'>I want to go to Italy this year. (Within this year as the limit)</div></li></ul>In these examples, we can see that 中（ちゅう）に is sometimes read/said as 中（じゅう）に. The basic rule for when to use ちゅう or when to use じゅう is as follows: 中（ちゅう）に - Expresses a very specific (usually small) amount of time/space, or something that is not always the same (an amount of time/space that can change, depending on the person/situation). This 'thing' that ちゅう highlights is usually a 'process', and therefore means that (A) is 'in the process' of happening. Examples - A meeting, class, visit to somewhere.<ul class='writeup-examples--holder'><li class='writeup-example'><div class='writeup-example--japanese'>食事（しょくじ）中（ちゅう）に電話（でんわ）がかかってくると、イラっとする。</div><div class='writeup-example--english'>It ticks me off when I get a phone call while I'm eating.</div></li></ul>中（じゅう）に - Expresses a predetermined amount of time/space that will always remain the same, regardless of the person/situation. Therefore, じゅう does not highlight a 'process', but focuses on the 'length' or 'space' itself. This tends to mean 'all throughout', as it focuses on the full amount of time/space. Examples - A day, year, house, town or country.<ul class='writeup-examples--holder'><li class='writeup-example'><div class='writeup-example--japanese'>ゴミが家（いえ）中（じゅう）に広（ひろ）がっていて、歩（ある）くスペースがない。</div><div class='writeup-example--english'>There is so much garbage throughout my house, that there is no room to walk.</div></li></ul><div class='writeup-caution'><div class='caution-header'>Caution</div>There is also a difference between 音読（おんよ）み (chinese readings of words), and 訓読（くんよ）み (japanese readings of words). じゅう is used more frequently with 訓読（くんよ）み - (今年中（ことしじゅう）, 夏休（なつやす）み中（じゅう）, 今晩中（こんばんじゅう）) ちゅう is used more frequently with 音読（おんよ）み - (水中（すいちゅう）, 会議中（かいぎちゅう）, 試合中（しあいちゅう）.</div></div>

Grammar Info

中(ちゅう)

During, While, Throughout, In the process of