homology

from The American Heritage® Dictionary of the English Language, 5th Edition.

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

from The Century Dictionary.

• noun In chem., the relationship which the members of a homologous series bear to one another.
• noun The state or character of being homologous; correspondence.
• noun In geometry, the relation between two corresponding figures lying in the same plane which are such that corresponding points are collinear With a fixed point called the center of homology, while corresponding lines intersect on a fixed line called the axis of homology.

from the GNU version of the Collaborative International Dictionary of English.

• noun The quality of being homologous; correspondence; relation.
• noun (Biol.) Correspondence or relation in type of structure in contradistinction to similarity of function; as, the relation in structure between the leg and arm of a man; or that between the arm of a man, the fore leg of a horse, the wing of a bird, and the fin of a fish, all these organs being modifications of one type of structure.
• noun (Chem.) The correspondence or resemblance of substances belonging to the same type or series; a similarity of composition varying by a small, regular difference, and usually attended by a regular variation in physical properties; , all members of the paraffin series. In an extended sense, the term is applied to the relation between chemical elements of the same group. Cf. Heterology.
• noun (Biol.) the higher relation which a series of parts, or a single part, bears to the fundamental or general type on which the group is constituted.
• noun (Biol.) representative or repetitive relation in the segments of the same organism, -- as in the lobster, where the parts follow each other in a straight line or series.
• noun (Biol.) the correspondence of a part or organ with those of a different animal, as determined by relative position and connection.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A homologous relationship.
• noun biology A correspondence of structures in two life forms with a common evolutionary origin, such as flippers and hands.
• noun chemistry The relationship between the elements in the same group of the periodic table, or between organic compounds in a homologous series.
• noun mathematics A theory associating a system of quotient groups to each topological space.
• noun mathematics A system of quotient groups associated to a topological space.
• noun genetics The presence of the same series of bases in related genes.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the quality of being similar or corresponding in position or value or structure or function