～ちゃう and difference between two tries

Hello! Lately I have seen some verbs that ~chau on the end and I'm not sure what it means. I heard an example, 辞めちゃったんだ, or 'I quit my job.' What is this ~chau?

Also, if anyone could sort out the difference between the two tries for me, that would be great. By this I mean, Base 5 + to omou, and ~te + miru.

彼は寿司を食べようと思いました。he tried to eat the sushi.
彼は寿司を食べてみました。 he tried to eat the sushi.

ちゃう is the contraction of ～てしまう.

辞めちゃったんだ ＝ 辞めてしまったんだ


"He tried to eat the sushi" is close to 彼は寿司を食べようとしました. 彼は寿司を食べようと思いました。 is more likely for "He thought to eat the sushi."

彼は寿司を食べてみました means "he tried eating the sushi". ～てみた is used for "actually did".

～ちゃう＝～てしまう means completion, and often with feelings (regret, etc.)
仕事を辞めた : I quit the job. (neutral statement )
仕事を辞めてしまった、止めちゃった: I've quit the job (already/though I intended to stay longer, etc.)

彼は寿司を食べてようと思いました。he thought we would try to eat the sushi (so you do not know whether he actually tried it out or not.)
彼は寿司を食べてみました。 he tried to eat the sushi.

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Ooops, Toritoribe san beat me!

undrentide said:

～ちゃう＝～てしまう means completion, and often with feelings (regret, etc.)
仕事を辞めた : I quit the job. (neutral statement )
仕事を辞めてしまった、止めちゃった: I've quit the job (already/though I intended to stay longer, etc.)

彼は寿司を食べてようと思いました。he thought we would try to eat the sushi (so you do not know whether he actually tried it out or not.)
彼は寿司を食べてみました。 he tried to eat the sushi.

---
Ooops, Toritoribe san beat me!

Click to expand...

トリトイベさん、ウンヅレンタイドさんお答えをどうも ありがとう。

I had some previous knowledge of ~te + shimau, so learning that this chau was a contraction was simple and helpful! I assume that with yodan verbs, it is base 2 + chau (oyogichau, kakichau, yakusoku shichau). Is it also possible to use the te form and just replace shimau with chau (oyoide chau, kaite chau, yakusoku shite chau)?

Also, I noticed in your examples Undrentide, you use tabete you to omoimashita as opposed to tabeyou to omoimashita. Is there a correct usage or are both acceptable? I haven't even begun to touch the various uses of 'you' that I've seen around.

～てしまう refers to "the -te form of a verb + しまう", and not "the -masu stem of a verb + てしまう". ～でしまう is contracted to ～じゃう.

泳ぐ --> 泳いでしまう --> 泳いじゃう
書く --> 書いてしまう --> 書いちゃう
する --> してしまう --> しちゃう


食べてよう is the contraction of 食べていよう, i.e., the volitional form of ～ている form of 食べる.

泳ぐ --> 泳いでいる --> 泳いでいよう --> 泳いでよう
書く --> 書いている --> 書いていよう --> 書いてよう
する --> している --> していよう --> してよう

食べてようと思った can also mean 食べ始めていようと思った "thought to start to eat" or 食べ終わっていようと思った "thought to finish eating" depending on the context, besides what undrentide-san explained.