From Teflpedia

A colleague (/kɒli:g/) or co-worker (/kəʊwɜ:kə/) is a person whom you work with in a profession or business.

As an English teacher or researcher, your colleagues may be fellow ESL teachers or researchers, but they can also include cleaners, managers, receptionists, recruiters, salespeople, teacher trainers, HR managers, IT support technicians, etc.

Maintaining good relations with one’s colleagues is always a good idea. In a large organisation there will inevitably be some personality clashes, particularly with interesting characters.

Note students may confuse the word colleague (/kɒli:g/) with college (/kɒlɪʤ/), as they may be confused by the infrequent trigraph -gue.