日本語の「もう/まだ」を英語は3人で分担します。already =「もう(完了)」、yet =「まだ(未完了・否定と疑問で)」、still =「まだ(継続中)」。定位置も三者三様: already と still は文中(一般動詞の前、be 動詞・助動詞の後)、yet は文末が基本です(かたい書き言葉では The date has not yet been decided. のように not の直後にも立ちます)。
Japanese もう and まだ split three ways in English: already (done sooner than expected), yet (not done — negatives and questions), still (continuing). Their posts differ too: already and still sit mid-sentence, before a main verb and after be or an auxiliary; yet waits at the end, though formal writing lets it slide inward, as in The date has not yet been decided.
3人の分担表
The Three-Way Split
already は「予想より早く、もう済んだ」の驚き込み: I've already eaten.(もう食べたよ)。yet は「まだ済んでいない・もう済んだ?」の未完了担当で、否定文と疑問文の文末に住みます: I haven't finished yet. / Are you done yet? still は「前の状態がまだ続いている」: I'm still hungry.(まだお腹すいてる)。「完了した=already、未完了=yet、継続中=still」の3分割です。
Already carries a note of "sooner than expected": I've already eaten. Yet handles the not-done side, living at the end of negatives and questions: I haven't finished yet. Are you done yet? Still means the earlier state persists: I'm still hungry. Done = already; not done = yet; ongoing = still.
分担の実演The split, demonstrated
It's only nine and I'm already sleepy.
まだ9時なのに、もう眠い。
「予想より早い」の already。Sooner than expected — already.
Hasこの文の組み立て【現在完了】過去に起きたことを、いまと結びつけて言う形。「いつ起きたか」ではなく「いまどうなっているか」に重心がある。だから yesterday のような過去の一点を指す語とは一緒に使えない。（この文では 2 語はさまって離れている）theなぜ the なのか【その場で一つに決まる】話し手と聞き手のいる状況で、どれを指すか一つに決まるから the。日本語なら「（例の）」「うちの」を補って読むと感覚が近い。 bus left yet? — Not yet.
バスもう出た? ——まだだよ。
疑問の文末 yet と、返事の Not yet.。Question-final yet, answered by Not yet.
Are you still working at that café?
まだあのカフェで働いてるの?
継続の still。文中(be・助動詞の後)が定位置。Continuation still — mid-position, after the auxiliary.
not yet
「まだしていない」(いずれする含み)。中立の未完了。Not done — with "but it's coming" built in. Neutral.
I haven't decided yet.
まだ決めてないんだ。
still not
「いまだにしていない」(遅い、というじれったさ込み)。Still not done — impatience included.
"Not yet" belongs to yet, at the end of a negative sentence. Already lives on the done side — force it into a negative and you get a twisted "it's not that I've already done it." Negative + sentence-final = yet. Keep the frame.
Not yet.まだだよ。「もう〜した?」への定番の返事。2語で完結する。The two-word answer to every "done yet?" question.
as yet今のところはまだ書き言葉の yet。報告書・ニュースの「現時点では未」。Yet in business attire — reports and news.
better still / better yetさらに良いことに提案を一段上げる接続の慣用。still/yet の「その上」の顔。Raising the offer one notch — still and yet's "on top of that" face.
still going strong今も健在で継続の still の看板慣用。長寿・現役を讃える定番。Continuation still's flagship — saluting long runs.
まとめ / Summary
already =もう(完了・驚き込み)。文中に。Already: done, sooner than expected — mid-sentence.
yet =まだ(否定・疑問の文末。かたい文では not の直後にも)。返事は Not yet.。Yet: not done, final in negatives and questions (formal writing also puts it right after not).
still =まだ続いている。文中(be の後・一般動詞の前)。Still: continuing — mid-position (after be, before a main verb).
still not は「いまだに」のじれったさ込み。Still not adds the impatience.