加わる

1. to be added to
   彼が私達に加わるのは当然だと思った。We took it for granted that he would join us.

   彼が私たちに加わるかどうか私は知らない。I don't know whether he'll join us or not.
2. to be appended
3. to join in (e.g. a group of friends)
4. to participate
5. to increase (e.g. heat)

Conjugation