an associate that one works with
"Sarah greeted her colleague as they walked into the office together to start the day's meetings."
A fellow member of a profession, staff, academic faculty or other organization; an associate.
"My colleague from the accounting department helped me finish the report before the deadline."
In plain English: A colleague is someone you work with at your job or school on similar tasks.
"She asked her colleague for advice on how to finish the project before the deadline."
Usage: Use colleague to refer specifically to someone you work with in the same professional capacity rather than using it as a general synonym for friend. It is always used before a noun, such as "colleague from accounting," and never takes an article like "a" when standing alone at the start of a sentence unless preceded by another determiner.
To unite or associate with another or with others.
"The scientist decided to ally with his colleague to advance their shared research goals."
In plain English: There is no verb form of the word colleague because it only describes a person who works with you, not an action someone can do.
"I have no experience with colleagues being used as verbs since they are strictly nouns, so I cannot write that sentence for you."
The word colleague comes from the Latin collēga, meaning "a partner in office," which itself is built from a prefix meaning "with" and a root related to sending someone on an official mission. It entered English via Middle French, retaining its original sense of sharing a professional role or duty.