A colleague is someone you work with, especially in a professional setting. Teachers are colleagues with other teachers at their school. Scientists working in the same laboratory are colleagues. Doctors at a hospital are colleagues, even if they work in different departments.

The word suggests a relationship based on shared work rather than friendship, though colleagues can certainly become friends. Your colleague might be someone you collaborate with on projects, someone who works down the hall, or someone doing similar work in another city whom you meet at conferences.

Often, colleague implies a sense of professional respect and working on a similar level. People sometimes use the word broadly, and in many workplaces, a boss might call employees colleagues, and employees might call their boss a colleague too. The relationship between colleagues is different from that between friends: you might not choose to spend time with your colleagues outside of work, but you treat them with courtesy and work together effectively.

When someone says “my colleagues and I,” they're usually referring to people in their field or workplace who share similar responsibilities or expertise. A marine biologist's colleagues are other marine biologists and researchers. The word carries a sense of professional community: your colleagues are the people who understand the specific challenges and rewards of your work because they do similar work themselves.