間に|まに

1. 1Something happens while another state or activity is ongoing.Ex. 1
2. 2An action is completed within a given period.Ex. 2

Neutral in speech and writing, 間に places an event or accomplishment within a period. It focuses on when that event falls, whereas うちに often suggests an opportunity that may end when circumstances change.

• うちにN3「うちに」emphasizes that a state will change and you must act early (the preceding clause must be a changeable state), or it expresses an unnoticed change occurring while something continues (the following clause is a natural change). In 'while it's hot'–type cases, 「うちに」and「間に」are interchangeable, but for simply referring to a time span, 「間に」is the better choice.
• 最中にN3「最中に」is close in meaning only to the first sense of 「間に」: it more strongly emphasizes an activity in progress being interrupted by a sudden event, and it cannot express deliberately finishing something before a deadline. It attaches only to noun + の and the 「ている」form, never the dictionary form.
• 〜ないうちにN3「〜ないうちに」attaches only to the ない-form of a verb and usually means hurrying to do something before an unwanted situation arises, with the urgency that 'if you're late, it will be too late.' When expressing unnoticed change, 「知らないうちに」and「知らない間に」are interchangeable.
• ときN5「とき」simply points out the time or period when something happens, without emphasizing the span of time; 「間に」highlights that something happens within a bounded period or is completed before the period ends. Both are neutral in register.
• ところに / ところへN2「ところに/ところへ」does not set a time span; it pinpoints 'the very moment you are doing, are about to do, or have just done something,' when an external event such as a visit or a phone call happens to occur, adding a nuance of surprise or of being disturbed. The following clause cannot express volition or a request, and the pattern cannot replace the second sense of 「間に」.
• 際にN3「際に」refers to the occasion or situation for doing something, with a formal tone, and appears mostly in notices and procedural instructions; 「間に」marks out a bounded period for things that happen or are completed within it, and is neutral in register. The two are generally not interchangeable.

うちに often suggests acting before circumstances change, and 〜ないうちに means before something happens; 最中に emphasizes being in the midst of an activity, while ところに / ところへ marks a particular stage at which something happens or someone arrives. とき identifies a time or occasion, which may be extended, and the more formal 際に identifies an occasion; neither necessarily means a single moment.