1. The occurrence of greater species diversity and biological density in an ecotone than in any of the adjacent ecological communities.
2. A phenomenon, such as a sandhi rule or cliticization, that happens at the edges of words, phrases, or other linguistic units.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.