partner (someone that you do an activity with): My partners and I are setting up a new business. I need a dance partner.
colleague (someone you work with, especially in a company or organization): He is a colleague of mine.
co-worker US (someone you work with doing the same kind of job): Would you introduce me to your co-workers.
workmate UK (someone you work with doing the same kind of job): This man is my workmate.
associate (someone you work with, especially in business): We are close friends and business associates.
confederate formal (a person who joins someone do something secret or illegal): We have captured all your confederates.
