How to tell them apart
までに marks a deadline by which something must be completed or happens, focusing on a fixed point in time. うちに highlights an ongoing window or state that will not last, urging action before it changes. Swapping them is unnatural: you say 3時までに来てください for a deadline, not 3時のうちに来てください, and 若いうちに勉強する for趁着年轻, not 若いまでに勉強する.
- までに Use までに when you mean a specific deadline or point by which an action is completed.
- うちに Use うちに when you want to act during a limited window before a situation changes or ends.
| Grammar point | Meaning | JLPT level |
|---|---|---|
| までに madeni | no later than a set time or deadline | N4 |
| うちに uchini | during the time something holds; before the chance is gone | N3 |
までに madeni
no later than a set time or deadline
までに sets a deadline by which an action must be completed or a state reached, meaning 'by (a certain time)'. It follows a time expression or noun, often with の before it (明日までに, 来週の火曜日までに). Adding は, as in までには, emphasizes the deadline.
-
明日までに書かなければならないレポートがいくつかある。
I have a few essays to write by tomorrow.
-
明日までにその仕事を終えることはどうしてもできません。
I cannot possibly finish the work by tomorrow.
うちに uchini
during the time something holds; before the chance is gone
うちに means doing something while a state lasts or before it changes, often with the nuance that the chance will pass. It follows plain-form verbs, including negative forms like 忘れない, and can also follow a noun plus の. It is common in both casual and polite speech.
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忘れないうちに彼の住所を書き留めておかねばならない。
I must write down his address before I forget it.
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彼らはあまり遠くに行かないうちに１人の老人に会った。
They hadn't gone very far when they met an old man.
までに and うちに are JLPT N4–N3 grammar points that Japanese learners often mix up. This page compares them side by side on meanings, usage and example sentences, so you can tell them apart.