suffix
pluralizing suffix (people, animals)
Attaches to nouns and pronouns to indicate a group including the referent. Primarily used for people and animals; formerly had an honorific nuance, now neutral. Often written in kana.
子供たちが公園で遊んでいる。
The children are playing in the park.
私たちは明日、映画を見に行きます。
We are going to see a movie tomorrow.
Originally a honorific suffix that evolved into a plural marker. The exact historical derivation is uncertain, but it is now a standard grammatical element.