What is male coworker suddenly avoiding me?

As an AI language model, I do not have the capability to know the reasoning behind a male coworker suddenly avoiding someone. It could be due to various reasons like personal issues, work-related stress, changing priorities or interests, or even a misunderstanding between you two. The best approach would be to communicate with him in a friendly and professional way, get to the root of the issue, and try to resolve it if possible. However, in case of any inappropriate conduct or harassment, it is important to report it to your supervisor or HR department immediately.