Casual contractions you will hear constantly: てる, ちゃった, なきゃ, じゃん

The few regular sound changes that turn しているの into してんの, てしまった into ちゃった, なければ into なきゃ and じゃない into じゃん.

Ukeru notes · counts are from the current library (1,905 routines, 174,812 machine-transcribed lines) and update as it grows

Why the textbook forms sound stiff

Textbooks teach full forms because they are easy to take apart: している, してしまった, しなければならない, ではない, のです. Out loud, and especially in the fast back-and-forth of a comedy duo, those forms get squeezed. The squeezing is not random. A handful of regular sound changes do most of the work, and once you know them you can rebuild the full form in your head whenever a line goes by too fast.

The counts below come from machine-made transcripts of the 1,905 routines in our library, so read them as rough guides rather than exact figures.

ている becomes てる

The い of いる drops after the て-form. That is the whole rule. Some simple examples:

• 何をしている → 何してる (what are you doing)
• 読んでいる → 読んでる (reading)
• 知っていた → 知ってた (knew)
• 分かっていない → 分かってない (doesn't get it)

In our library, lines with てる outnumber lines with the full ている by about 11 to 1. The short form also survives inside polite speech: しています is often heard as してます. So てる is not rude. It is simply how the verb sounds at speaking speed.

てるの becomes てんの

The second change: る (and sometimes ら or れ) turns into ん right before an n-sound such as の or な. Stack it on top of the first change and you get the chain every learner eventually hears:

何をしているの？ → 何してるの？ → 何してんの？

The same rule explains わからない → わかんない and くれない → くんない, which is where 〜てくんない？ comes from. Said warmly, 何してんの？ is just "what are you up to?". Said sharply, 何やってんの！ is "what on earth are you doing?!", a classic reaction from a straight man to his partner. More on the 〜てんの？ page.

てしまった becomes ちゃった

Here て + しま fuses into ちゃ. There is a step in between, ちまう / ちまった, which you still hear as a rougher-sounding variant. Verbs whose て-form ends in で take the voiced version, じゃ. Simple examples:

• 食べてしまった → 食べちまった → 食べちゃった (ate it all / ate it by mistake)
• 読んでしまった → 読んじまった → 読んじゃった (finished reading / read it, oops)

The meaning does not change: either "completely" or "it ended up happening, sadly". 忘れちゃった is "I (went and) forgot". In our library, ちゃった／じゃった outnumbers てしまった by about 6 to 1. See 〜ちゃった.

The same fusion turns ては into ちゃ, so 食べてはだめ becomes 食べちゃダメ, the 〜ちゃダメ pattern. One trap: in Kansai speech, ちゃう also means 違う ("no, that's wrong"). If ちゃう stands on its own or starts a reply, as in ちゃうちゃう！, it is most likely that one.

なければ becomes なきゃ

Conditional ければ contracts in two steps: ければ → けりゃ → きゃ. Then the second half of the obligation phrase (ならない or いけない) usually disappears, because everyone knows how the sentence ends:

しなければならない → しなけりゃならない → しなきゃならない → しなきゃ

So もう行かなきゃ is "I've gotta go". Its sister form なくちゃ comes from なくては (ては → ちゃ again), and ないと, cut down from ないといけない, does the same job. In our library, なきゃ appears on 319 lines; the count for the full なければ is 50. The 〜なきゃ page has the scenes.

ではない becomes じゃない, then じゃん

では squeezes into じゃ, so ではない becomes じゃない. In our library, じゃない outnumbers ではない by about 25 to 1.

The catch is that じゃない does two different jobs:

1. Plain negation: 学生じゃない, "(I'm) not a student".
2. Pointing something out or asking for agreement: いいじゃない, "that's nice, isn't it?"; 言ったじゃない, "I told you, didn't I?"

Only the second job gets clipped to じゃん: いいじゃん, 言ったじゃん. So 学生じゃん does not mean "not a student". It means "you're a student, aren't you" or "see, you're a student". That one distinction clears up most confusion about じゃん, which appears on 2,039 lines in our library. The rough version of じゃない is じゃねえ (ない → ねえ), which is friends-only. Details on 〜じゃない.

のだ becomes んだ

の turns into ん before だ or で: のだ → んだ, のです → んです. This is the explaining, insisting form: 違うんだよ, "no, you don't get it". In our library, んです appears on 5,776 lines and the explaining のです on 109. Unlike some of the others, this one is completely standard, and んです is fine at work. The casual 〜んだよ adds an insisting or complaining edge.

How they stack

Real lines often combine several changes at once. Simple examples:

• 何をしているのだ → 何してるんだ → 何してんだ (い drops and の becomes ん, then るん merges into ん)
• 忘れてしまっていた → 忘れちゃってた (ちゃう, then い drops)
• 見てはいけないのだ → 見ちゃいけないんだ (ては → ちゃ, の → ん)

Using them yourself

Contractions signal speed and closeness, not rudeness. てる, ちゃった and んです sit comfortably inside polite ます speech: 見てます, 忘れちゃいました, 行かなきゃいけないんです are all normal things to say to a coworker. The rough edge comes from other pieces, like ねえ endings (じゃねえ), だろ or bare commands. In business email and formal writing, go back to the full forms.

For listening, the trick is to run the rules backwards. When you hear an ん where you expected a syllable, try putting る or の back. When you hear ちゃ or じゃ after a verb, try てしま or ては.

Try it

• Search the library for てんの, ちゃった, なきゃ or じゃん and try to rebuild each line's textbook form.
• Then watch the scenes on 〜てんの？, 〜ちゃった, 〜なきゃ, 〜じゃない and 〜んだよ, and say each line out loud at full speed.