General Meaning: Together, jointly, with, or in common
* co-author: A person who writes a book or article with another person.
* co-operate: To work together towards a common goal.
* co-ordinate: To organize and arrange things or people in a harmonious way.
* co-exist: To live together peacefully or harmoniously.
* co-founder: One of the people who started an organization.
* co-worker: A person who works with another person in the same workplace.
* co-star: An actor who appears in a film or play with another well-known actor.
* co-sign: To sign a document with someone else.
Specific Meanings
* co-educational: Involving both male and female students.
* co-owner: A person who owns part of something with another person.
* co-pilot: A person who helps the pilot of an aircraft.
* co-pay: A fixed amount of money paid by a patient for each medical visit or service.
Other Examples:
* co-dependent: A person who relies on or needs another person in a way that is unhealthy.
* co-efficient: A numerical factor that multiplies a variable.
* co-linear: Lying on the same line.
* co-habitation: Living together as a couple without being married.
* co-extensive: Covering the same area or having the same scope.
This is just a small selection of words with the prefix "co-". There are many more!