内(うち)にWhile, During

ながら attaches to verb stems to express performing one action simultaneously with another, e.g. 音楽を聴きながら走る 'listen to music while running'. In contrast, うちに can follow various words or phrases to express doing something while a certain state or condition persists, e.g. 若いうちにマラソンを走りたい ('I want to run a marathon while I'm young.').

ているところだ conveys that an action is in progress at that moment, with the nuance that the speaker is occupied with it, e.g. 晩ご飯を食べているところだ ('I'm in the middle of eating dinner.'). In contrast, うちに describes doing an action while a certain state is ongoing, often with the nuance that it's the ideal time, e.g. 熱いうちに食べましょう ('Let's eat it while it's hot.').

Both expressions refer to a continued state, but in different ways. うちに means 'do (B) while (A),' that is, during the ideal time or condition for (A), e.g. 熱いうちに食べてね ('Eat it while it's hot.') In contrast, 中 attaches to nouns and simply means 'during (A)' or 'in the middle of (A)', e.g. 会議中 ('in the middle of a meeting'), 授業中に携帯が鳴った ('My phone rang during class.')

Both can be translated as 'while', but differ in nuance. うちに emphasizes doing something before a condition changes, e.g. 熱いうちに食べてね ('Eat it while it's hot.') 最中に highlights something occurring in the very middle of another action, e.g. 会議の最中に電話が鳴った ('The phone rang in the middle of the meeting.')

Both の間に and うちに can express 'while' or 'during', but are used in different contexts. の間に simply conveys the idea of 'while (A), (B)', e.g. 映画を観ている間に眠ってしまった ('I fell asleep while/during watching a movie.') In contrast, うちに carries the nuance of doing something during an ideal time or condition, e.g. 明るいうちに帰ろう ('Let's go home while it's light out.')

Both can be translated as 'while', but with different implications. ついでに means 'while you're at it' and adds a convenient extra action, e.g. 買い物のついでに銀行に寄った ('I stopped by the bank while shopping.') うちに emphasizes doing something before a condition changes, e.g. 熱いうちに食べてね ('Eat it while it's hot.')

うちに means 'while' a state persists, implying that an action is taken during that time, e.g. 明るいうちに帰る ('Go home while it's still light.') ないうちに means 'before' a negative state ends, emphasizing the importance of acting before something happens, e.g. 雨が降らないうちに出かける ('Leave before it rains.') Both suggest taking action while a condition remains unchanged.

とき expresses the time of an action or event, like 'when' in English. It can be used with nouns as in 雨の時 'when it rains', verbs as in 父が帰ってきた時 'when Dad came home', or adjectives as in 暑い時 'when it's hot', and can describe one-time or repeated actions. うちに means 'while' or 'during,' often with the nuance that it's the ideal or only time to act, e.g. 熱いうちに食べてね ('Eat it while it's hot.').

Both patterns can express the idea of 'while,' but differ in nuance. ているあいだに refers to something happening during another ongoing action. For example, 勉強しているあいだに電話がかかってきた means 'The phone rang while I was studying.' うちに emphasizes doing something while a particular state still lasts. For example, 早いうちに帰ろう means 'Let's go home while it's still early.'