Difference between 間 and 間に

Question

I have some problems with understanding what is the difference between these two. According to 初級日本語, 間 refers to certain time frame whereas 間に refers to certain time frame within that time frame. Is it correct or am I missing something?

Answer 1

It is very simple:

A 間　B　

means;

All the time that A took place B was also happening. (I read my book while it was raining)

A 間に　B

means;

While A took place B happend. The nuance to appreciate is that B is an event that occurred (started & finished) at some point during the period A took place. It did not go on all the time. (While it was raining the post was delivered.)

The nuance is very similar to the difference between まで and までに

A　まで　B

means;

Until A happens, B will continue, constantly (I was watching television until father came home)

A　までに　B

means;

By the time A happens B will have occurred (started and finished, during the period defined by A まで; it could happend at any point but did not happen constantly. (I will finish my work by 5 o'clock. ie at some unspecified point during the period to 5'oclock)

Answer 2

I've summarized the following from a Dictionary of Basic Grammar which seems a little different from what you state. (Note that I'm not a native speaker.)

The time span in the clause before 間 and the main clause is the same, whereas the time span in the clause before 間に is wider than the time span of the main clause.

For example:

山田さんが巴里｛パリ｝に留学している間にお母さんが病気になった。

The period in which she became sick is a portion of the time when Yamada was studying in Paris. If 間に is replaced by 間 then the sentence becomes ungrammatical according to A Dictionary of Basic Grammar.