noun
A person who regularly travels between home and work or school, typically by train or bus.
朝のラッシュ時には多くの通勤者で駅が混雑する。
During the morning rush hour, the station is crowded with many commuters.
通勤 is the act of commuting, whereas 通勤者 is the person who does it.
Compound of 通勤 (commuting) + 者 (person).