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I just decided I needed to know the word for week and found both 週 and 週間 mean
"week".

Can I get by as a beginner with only 週間? Or when should each one be used?
CC BY-SA 4.0
2019-05-14T02:29:37.013
68209
2019-05-17T01:46:36.403
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question
word-choice synonyms
When should I use 週 versus 週間 for "week"?
For beginners, I recommend the following:

  * Use `週` when you specify a week. e.g. `第5週` = the fifth week
  * Use `週間` when you refer to a time span. e.g. `5週間` = five weeks.

This is preferable while you may `週` instead of `週間`.
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2019-05-14T03:25:17.567
68211
2019-05-14T03:25:17.567
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answer
You should know both, and their differences.

Measures of time are often suffixed with -間, and in the case of a measure of
time with weeks as the unit, -週間 is the preferred way to say "week" as in "an
interval of X weeks".

For example:

> 一週間 = one week's time (or more colloquially, one week)
>
> 卒業式まであと(残り)わずか一週間です。(or 卒業式まであと一週間しかありません。)  
>  There's only one week left until the graduation ceremony.

When speaking of a point in time that is a relative point in time, you would
use just -週 as the word for "week".

For example:

> 来週 = next week
>
> 来週の月曜日は僕の誕生日なんです。  
>  Next week Monday is my birthday.

So, 週 is "week" in a relative sense, while 週間 is "week" in a quantifiable
sense. Neither of these words would completely serve on their own, as they
usually form a part of another word that provides clearer context, but knowing
what context they provide to a word helps with determining how you'll use
them.
CC BY-SA 4.0
2019-05-16T21:11:49.217
68293
2019-05-17T01:46:36.403
2019-05-17T01:46:36.403
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answer