Explanation
Use "until" when an action continues up to a time. Use "by" when you mean a deadline.
For example, "Please finish the homework by 8 o'clock." Here "Please" makes it polite, "finish the homework" is the action, and "by 8 o'clock" means no later than 8. Compare that with "Please wait until 8 o'clock." That means keep waiting up to 8, and then stop. In Japanese, both often become "まで", so the difference is easy to miss.
"until" は、ある動作がその時点まで続くときに使います。"by" は、締め切りや期限を言うときに使います。
例えば "Please finish the homework by 8 o'clock." では、"Please" が丁寧さを出し、"finish the homework" が行動、"by 8 o'clock" が「8時までに、遅くとも8時までに」という意味です。これに対して "Please wait until 8 o'clock." は、8時まで待ち続けて、8時で終わるという意味です。日本語ではどちらも「まで」になりやすいので、混同しやすいです。
Examples
- Please wait until I call you. 私が電話するまで待ってください。
- The shop stays open until 9 p.m. その店は午後9時まで開いています。
- I have to send this by Friday. これを金曜日までに送らないといけません。
- Can you finish it by noon? 正午までに終わらせられますか。
- We did not leave until it stopped raining. 雨がやむまで私たちは出発しませんでした。
- Don't eat it until I get back. 私が戻るまで食べないでください。
Common Mistakes
Japanese learners often use "until" for deadlines because "まで" feels the same.
Wrong: "Please submit it until Friday."
Right: "Please submit it by Friday."
Use "until" for something that continues, and use "by" for a deadline.
日本語ではどちらも「まで」なので、締め切りにも "until" を使ってしまいやすいです。
誤り: "Please submit it until Friday."
正しくは "Please submit it by Friday."
続く動作には "until"、期限には "by" を使います。