colleague (n.)

• ace
• adjunct
• aide
• ally
• amigo
• assistant
• associate
• bedfellow
• brother
• buddy
• bunkmate
• butty
• chum
• classmate
• co-worker
• coadjutor
• cohort
• companion
• company
• compatriot
• compeer
• comrade
• confederate
• confrere
• consort
• copartner
• crony
• fellow
• gossip
• helper
• mate
• messmate
• pal
• pard
• pardner
• partner
• playfellow
• playmate
• roommate
• schoolfellow
• schoolmate
• shipmate
• sidekick
• teammate
• workfellow