I am doing this exercise from wasabi-jpn.com. The exercise includes this sentence:

The sweater (I) bought last week was expensive.

Apparently, the correct answer is


I realize that the particle は cannot be used after 先週 because it's a relative clause, but why there is no particle at all?

  • 4
    What particle were you thinking could go there?
    – Leebo
    Commented Jul 18, 2020 at 23:40
  • @Leebo が. My thinking process was this: the full sentence would be 先週はセーターを買いました, so to make it a relative clause I need to change は to が. I also assumed that if が is incorrect than some other particle should be used, and I simply don't know the correct rule for this yet.
    – ash
    Commented Jul 19, 2020 at 11:14

1 Answer 1


Firstly, using the particle が would make no sense at all. が marks the subject of a verb, so 先週セーターを買いました would mean that "last week bought a jumper". Unless you have some bizarre world where you have anthropomorphised the weeks then this sentence is pure gibberish.

は and が are not interchangeable (see this). は can mark a subject, but it does not do so in this case. The subject in this sentence is the hidden/implied "I".

Adding は to 先週 denotes that either 'last week' is the topic of the sentence, or that you are contrasting last week with some other time see this post.

Finally, you are right that は is not normally allowed in a relative clause, but there is an exception. は can be retained if it is used as a contrast marker rather than as a topic (see this post).

In conclusion, no particle is needed in either the full sentence above or in the sentence which is just the relative clause.

  • I see. I got so used to seeing 先週は、今日は、明日は etc. in beginner lessons that I never questioned why exactly は was used here. This clears my confusion on all points. Thank you!
    – ash
    Commented Jul 21, 2020 at 13:17

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