Are they interchangeable, or is 昨週 an old way to say it, and not used as much
any more?

> 昨週レストランに友だちと行った。

If anybody knows any kind of nuances or differences, such as where one would
be more appropriate, it would be interesting to know. Thank you very much!
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2015-12-29T10:10:12.630
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words
昨週 - when is it used? (compared with 先週)
`昨週` is in a dictionary, but I have never heard the word. While
`昨週レストランに友だちと行った` is not necessarily incorrect, I think `先週` is the most
natural word for any instance. It's also confirmed by search results in
Google:

  * `先週` 24,800,000 results
  * `昨週` 11,200 results

There are no difference between `先週` and `昨週` in meaning. `昨週` does not seem
to be old-fashioned. It's just a rarely-used word.
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2015-12-29T13:59:25.263
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2015-12-29T14:49:02.183
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昨週, reads saku-shuu, is a noun. It's simply not used in the language, even if
it can be translated as "last week" as 先週, reads sen-shuu, which is an adverb.
The kanji 昨 is used to say "yesterday" though, in the word 昨日, reads kinou.
When you are talking about somebody you pay your respect to and/or you like to
be more polite to the person your are speaking to, you read 昨日 as saku-jitsu.
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2015-12-29T14:47:10.490
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昨 mean (the) last. 昨日 means 'yesterday,' 昨週 means 'last week.' 昨週 and 先週 is
the same thing, but we seldom hear the former (昨週) these days. In written
form, it looks natural. In colloquial form, it sounds too stylish and awkward.
We say 昨年、昨夏、昨晩、likewise. 昨年 is common as well as 去年。 昨夏、昨晩 sound stylish and
a bit outdated as compared with 去年の夏、昨日の夜 to me. But that's my personal
opinion.
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2015-12-31T00:07:04.740
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