Complementors is a term used to describe businesses that directly sell a product (or products) or service (or services) that complement the product or service of another company by adding value to mutual customers; for example, Intel and Microsoft

Microsoft

Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

 (Pentium processors and Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

), or Microsoft and McAfee

McAfee

McAfee, Inc. is a computer security company headquartered in Santa Clara, California, USA. It markets software and services to home users, businesses and the public sector. On August 19, 2010, electronics company Intel agreed to purchase McAfee for $7.68 billion...

 (Microsoft Windows & McAfee anti-virus).

Complementors are sometimes called "The Sixth Force" (from Porter's Five Forces model), a term which was coined by Adam Brandenburger.

Before its use in business, the word was used to describe a color that is complementory to another color.