I know that 'co-worker' and 'colleague' are both used in the US (I'm American) and I am pretty sure that both are used in the UK as well. (I work with lots of Brits.) As others have said, 'colleague' is a more formal or fancy word than 'co-worker.' To give an example, if you work at McDonald's you have co-workers. If you are an executive at a big corporation you have colleagues. People in big corporations sometimes say 'co-worker' or 'colleague.' But if you are working in a fast food restaurant, you would only say 'co-worker.' Jason also makes a good point. 'Colleague' can mean someone you know who works for a different company in the same industry or field. For example, if you are a lawyer for Company X, then you might refer to a lawyer at Company Y as your colleague.

I use both words (as an American), but in different ways. There are people that I work with at my office, they are my co-workers. There are people that work in the same field as me, that do not work at my office, but I know them, and we have work-related things in common. I often have to work with, or attend conferences with them. These are my colleagues. Lorraine is correct that most English speakers would understand you if you used either word, but their meaning is not exactly the same.

They have basically the same meaning but tend to be used in different circumstances. Colleague is more business oriented for people who work in companies or professions. Co-worker is used more for people who work in non professional fields such as in department stores, restaurants, service jobs, etc... Cheers!

Normally yes however if you used either word in America or England the person will understand what you are saying.

Good question!