ちゃう

Contraction of 〜てしまう (-te shimau).^[1][2][3]

/-te ɕimau/ → /-t͡ɕimau/ → /-t͡ɕau/

ちゃう • (-chau) 

1. (colloquial) contraction of 〜てしまう

Attaches to what would be the regular -te form for the verb. Examples:

• 書く (kaku) → 書いて (kaite) → 書いてしまう (kaite shimau) → 書いちゃう (kaichau)
• 待つ (matsu) → 待って (matte) → 待ってしまう (matte shimau) → 待っちゃう (matchau)

If the regular -te form of the verb results in voicing from -te to -de, that voicing carries over to the abbreviated form.

• 呼ぶ (yobu) → 呼んで (yonde) → 呼んでしまう (yonde shimau) → 呼んじゃう (yonjau)

• ちまう (chimau)
• (Kansai) てまう (temau)

Contraction of 違う (chigau).

/t͡ɕiɡau/ → /t͡ɕau/

ちゃう • (chau) intransitive

1. (colloquial, Kansai) synonym of 違う (chigau)
2. (colloquial, Kansai) synonym of じゃない (ja nai)

   野(や)菜(さい)はあまり好(す)きちゃう

   yasai wa amari suki chau

   don't really like vegetables

The contracted form is limited to the 終止形 (shūshikei, “terminal or predicate form”) and 連体形 (rentaikei, “attributive form”), appearing in the 常体 (jōtai, “plain form, dictionary form”) of ちゃう (chau) and the 敬体 (keitai, “polite form, masu form”) of ちゃいます (chaimasu).

Used in a famous Kansai dialect pun, punning on ちゃうちゃう (chauchau, “Chow Chow (dog)”), ちゃうちゃう (chau-chau, “no, no”), ちゃう (chau, “isn’t it?”), and ちゃう (chau, “no (it isn’t)”). One variant is:

ちゃうちゃうちゃう？

Chauchau chau?

Isn’t that a chow chow?

ちゃうちゃう、ちゃうちゃうちゃう。

Chau-chau, chauchau chau.

No no, it’s not a chow chow.

• 関西弁が分かる方に質問です。 Ａ「あれ、ちゃうちゃうちゃう？」Ｂ「ちゃうちゃ... – one version of the pun