を

In a sentence

• 私は映画を見ます。

  I watch a movie.

  In this sentence, 'を' marks '映画' (movie) as the direct object of the verb '見ます' (watch).

• 友達を駅まで送ります。

  I take my friend to the station.

  Here, 'を' indicates that '友達' (friend) is the direct object being acted upon by the verb '送ります' (take).

• 川を渡ります。

  I cross the river.

  In this usage, 'を' specifies '川' (river) as the location traversed by the action of the verb '渡ります' (cross).