1. The quality or condition of being homologous.
2. A homologous relationship or correspondence.
3. Chemistry.
   1. The relation of the elements of a periodic family or group.
   2. The relation of the organic compounds forming a homologous series.
4. Mathematics. A topological classification of configurations into distinct types that imposes an algebraic structure or hierarchy on families of geometric figures.

[Greek homologiā, agreement, from homologos, agreeing. See homologous.]

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.