うちに・
Something is true now and won't last: the soup is hot, you are a student, it isn't dark yet. うちに marks what gets done, or what changes, while it is still true. After ない, English says "before".
while it lasts
Please have the soup while it is still warm.
before it changes
Let's go down the mountain before it gets dark.
little by little
As I kept listening to the radio every morning, I gradually got used to fast Japanese too.
Verb
Verb (usually ている) + うちに
寝ているうちに. いる goes in as it is: 日本にいるうちに.
Negative
Verb in the ない-form + うちに
忘れないうちに, 暗くならないうちに. This is "before".
Adjective
い-adjective + うちに
若いうちに. A な-adjective takes な: 元気なうちに.
Noun
Noun + の + うちに
学生のうちに, 今日のうちに.
While you still can
The second half is usually something to do before the chance is gone: a plan, a wish, a request.
While I'm still a student, I'd like to try some classes outside my field too.
The shop is closed tomorrow, so let's buy food today while we can.
うちに or 間に?
I finished preparing for tomorrow while the child was asleep.
When it got done, and no more.
I finished preparing for tomorrow while the child was still asleep.
The same, with the hurry in it: the child was going to wake up.
間に only says when. うちに adds that it won't last. With an adjective or ない, うちに is the usual one: 若いうちに, 冷めないうちに.
ないうちに is "before"
The first half hasn't happened yet, and you act while that is still true. English says "before it rains". Japanese says "while it isn't raining", so the verb is negative.
Let's walk to the station before it starts raining.
Not said: 雨が
(Let's walk to the station before it starts raining.)
It is mostly for what comes whether you like it or not: rain, nightfall, forgetting, food going cold.
前に or ないうちに?
Let's go down the mountain before it gets dark.
Plain "before": the order and nothing more.
Let's go down the mountain before it gets dark.
The same, with the hurry in it: after dark it will be too late.
Little by little: ているうちに
The other use has no hurry in it. While something went on, a change crept in: you got used to it, you understood, you fell asleep.
As I read it again and again, I came to see what makes this poem interesting.
I fell asleep watching TV.
Not for how things were
English "while" also covers how things simply were at the time. うちに doesn't: that is とき.
Not said: 学生の
(While I was a student, I had no money.)
Nothing got done and nothing changed: 学生のとき、お金がなかった.
Things people say
今のうちにnow, while you can
Go to the bathroom now, while you can.
冷めないうちにbefore it gets cold
Please start, before it gets cold.
What a host says when the food is on the table.
忘れないうちにbefore I forget
I'll send the email now, before I forget.
知らないうちにbefore I knew it
Three hours had gone by before I knew it.
近いうちにsoon, one of these days
Let's meet again soon.
Close neighbours
間にN4
No hurry in it. A sudden event in the middle of something, like the phone ringing, takes this one.
The phone rang while I was taking a shower.
前にN5
Plain "before": the order and nothing more. Something you do yourself, by plan, takes this one.
I read a little before going to bed.
Check yourself
1Which one fits?
店が
Choose an answer to see why.
2Which sentence sounds natural?
Choose an answer to see why.
3What does this say?
日本で
Choose an answer to see why.
More detail
うちは
With は it is "as long as": this stretch, set against what comes after.
As long as you are a student, you have plenty of time.
More sentences
While I'm still young, I want to take on challenges without being afraid to fail.
I want to visit Kyoto while I am still in Japan.
Would you like to go and take pictures before the cherry blossoms fall?
As I kept practicing, I gradually became more confident.