Doing and done
Four -te auxiliaries that set the shape of an action: ongoing, tried out, finished, done ahead.
-teru
polite -temasuis doing / is in a state
〜てる 〜てます
Attaches to the -te form for an ongoing action (tabeteru), a resulting state (kekkon shiteru, shitteru) or a habit; it is the casual contraction of -te iru.
ima repooto kaiteru.
I'm writing a report right now.
今レポート書いてる。
ima repooto kaitemasu.
I'm writing a report right now.
今レポート書いてます。
With change verbs it's a state, not progress: kekkon shiteru = is married. Trap: the negative of shitteru is shiranai, not *shittenai.
-te miru
polite -te mimasutry (and see)
〜てみる 〜てみます
Attaches to the -te form to try something out and see how it goes (tabete miru, kiite miru), which also softens plans and suggestions.
jaa, tabete miru.
OK, I'll give it a try.
じゃあ、食べてみる。
jaa, tabete mimasu.
OK, I'll give it a try.
じゃあ、食べてみます。
Not 'attempt and fail': you actually do it to find out.
Learn first: -te
-chau
polite -chaimasuend up / do completely
〜ちゃう 〜ちゃいます
Contracted -te shimau, marking something done completely, often with regret or an 'oops' (wasurechatta, tabechatta); -nde verbs take -jau (nonjatta).
repooto, mou kaichatta.
I've already finished the report.
レポート、もう書いちゃった。
repooto, mou kaichaimashita.
I've already finished the report.
レポート、もう書いちゃいました。
The regret reading is the everyday one: saifu wasurechatta = I forgot my wallet (ugh). Not -cha (= -te wa): kaetchau = I'll end up going home, kaetcha dame = you can't go home. -chaimashita is friendly-polite; with superiors or strangers use -te shimaimashita.
-toku
polite -tokimasudo in advance; leave it
〜とく 〜ときます
Contracted -te oku, for doing something now so it's ready later (kattoku) or leaving it as it is (sono mama ni shitoite); -nde verbs take -doku (yondoku).
repooto, saki ni kaitoku.
I'll get the report written first.
レポート、先に書いとく。
repooto, saki ni kaitokimasu.
I'll get the report written first.
レポート、先に書いときます。
Not -teku (-te iku): kaitoku = write it now so it's done, kaiteku = write it before heading off. Past -toita (kaitoita) sits close to -teta (kaiteta); listen for the o.