Colleague
Coworker
noun
We work at the same place and are colleagues, making us colleagues / coworkers.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
残念な事に、私の同僚はあの電車の事故によって大きな商談のスケジュールの組み直しを余儀なくされた。
Unfortunately, the train accident forced my coworker to rearrange his big business meeting.