For example, what makes 相手になる different from 相手にする. I know that 「~になる」 is to be/become something, and 「~をする」 is to do something, but what does each imply when used?

  • (The 相手 in 相手になる is the subject, and the 相手 in 相手にする is the object... as you might know...) Are you asking about 「~"に"する」 or 「~"を"する」?Because the 相手 in 相手にする and 相手をする are not the same person.
    – user1016
    Feb 11, 2013 at 0:33
  • @Chocolate: this is an ill-chosen example I think. The question seems to be about adverbs so I used a different adverb in my answer.
    – user18597
    Feb 11, 2013 at 0:33
  • 2
    Oh.. I think 相手に isn't an adverb but.. is 暖かく an adverb?
    – user1016
    Feb 11, 2013 at 0:40
  • 3
    By "The 相手 in 相手になる is the subject, and the 相手 in 相手にする is the object", I meant to say-- "In 'AがBの相手になる', A becomes the 相手. In 'AがBを相手にする', B becomes the 相手." (And, in 'AがBの相手をする' A becomes the 相手.) Here, になる is like "to become~", and をする is like "to play a role as~" and にする is like "to make~"
    – user1016
    Feb 11, 2013 at 0:53

1 Answer 1


Suru is active and implies somebody does something, but naru is passive and implies something happens. For example:

暖かくする / atatakaku suru = make it warm
暖かくなる / atatakaku naru = get warm.

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