うち （内） means inside. so this is "inside the time" or while.
I found this helpful: うちに indicates a period of time WITHIN WHICH an action occurs, and corresposnds to English "while still", or in negative constructions "before".
It is different to あいだ, which indicates a period DURING OR THROUGHOUT WHICH an action occurs, and is equivalent to English "while".
学生のうちに、よく勉強ひておきなさい。 Study hard while you are still a student.
Different to: 学生の間に、いろんな所を、旅行するつもりです。 I plan to travel to lots of places during the time I am a student.
うちに is also used to indicate an event building up or reaching a climax AS some action is being done.
先生の話を聞いているうちに、眠くなってきた。 I grew tired as I listened to the teacher speak.
Another way to keep うちに and あいだ apart is:
うちに: An abstract timespan with diffuse start and end time; e.g. childhood, rainy season
あいだ: A timespan where you can pinpoint start and end time; e.g. lecture, summer holiday
amega furanai uchini uchihe detekudasai
In ex. #3160 【彼は】みるみるうちに太った。 Could be "He gained weight in the blink of an eye" too?
Minutiaeさん> Please correct the notes: 勉強ひて->勉強して as in ex#6184. Why are they 2 different grammar entry うちに+うちに-2? In my point of view: One use of うちに describe a progressive change in the 2 clauses before and after うちに. This use is associated with progressive form of verbs like Vテ+行く(change in the future) and Vテ+来る(change in the past) or sudden change like Vイ+出す and Vイ+始める. In this use, うちに cannot be substituted by あいだに. These examples like ex #3160 are the best for [uchini]. The other use of うちに make an opposition between a temporary state in the clause before うちに which permits the clause after うちに, and the end of this temporary clause when it will be too late. This use should be in [uchini-2] but there are various example here in [uchini]. I think it will be great to rearrange these 2 entry. So I moved Ex #6186 from here to #6903 of [uchini-2] and I changed it with the example from the notes which fits better.
Is it just me or does 学生の間に seem a little unnatural? I cannot put my finger on it, but maybe if the sentence included the subject. 僕が学生の間に 色々な所へ行くつもりです or maybe this is a good place for 時 or にを消したら? 僕が学生の間 色々な所に行くつもりです 僕が学生の時に色々な所に行くつもりです I don`t know what it is, but that example just doesn`t seem natural.
isnt ex #6184 an example for the other 'UCHI NI' meaning 'before it stops'?
Whoops! Bad typo. Thanks for alerting me to it.
#6183 Please change from これど to これで.
暇なうちに does not mean "whenever you're free". "Whilte you are free" would be better. Just correct the latter part.
Yes it certainly sounds pretty weird in English. I think zio's translation is probably the most natural sounding translation of that sentence.
Wouldn't #3156 mean something more like "please come visit whenever you're free". I'm not a native English speaker, but er, "come here and play with me" has kind of a wrong sound to it, doesn't it?