Definition of "co-" [co-]

• Together; joint; jointly; mutually: coeducation. (prefix)
• Partner or associate in an activity: coauthor; cofounder. (prefix)
• Subordinate or assistant: copilot. (prefix)
• To the same extent or degree: coextensive. (prefix)
• Complement of an angle: cotangent. (prefix)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Though he retired from Bain in February 1999, Romney, 64, continues to benefit from the firm's profitable private equity funds and to invest alongside them in so-called "co- investment" vehicles, both of which generate income taxed at the 15 percent rate."
• "A Dangerous Method is a Canadian/German co- production."
• "Next among the six comes Dustin Moskovitz, a co- founder."