Complementary Distribution- "The occurrence of speech sounds in mutually exclusive contexts." In other words, two similar sounds, or "phonetically similar segments" have an exclusive relationship with each other. These segments should never occur within the same environment. The following explanation is a helpful way of looking at it. For more information please refer to http://web.stanford.edu/dept/linguistics/cgi-bin/website/resources/ta-manual/complementary-distribution.html. "Think about a soccer team: Each player standing on the field has her own ‘environment’ where she waits for the kickoff. This environment is the territory where she launches an offensive strategy, and the territory that she defends when the opposite team is approaching her team’s goal. She may be the goalie, or the fullback, or right halfback. Her position or territory is defined relative to the center line and right or left halves of the field, or relative to her team’s goal.