Source : Webster's Revised Unabridged Dictionary (1913)

Propane \Pro"pane\, n. [Propyl + methane.] (Chem.)
   A heavy gaseous hydrocarbon, {C3H8}, of the paraffin series,
   occurring naturally dissolved in crude petroleum, and also
   made artificially; -- called also {propyl hydride}.

Homology \Ho*mol"o*gy\, n. [Gr. ? agreement. See {Homologous}.]
   1. The quality of being homologous; correspondence; relation;
      as, the homologyof similar polygons.

   2. (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.

   Note: Homology indicates genetic relationship, and according
         to Haeckel special homology should be defined in terms
         of identity of embryonic origin. See {Homotypy}, and
         {Homogeny}.

   3. (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; as, there is an homology between methane,
      {CH4}, ethane, {C2H6}, propane, {C3H8}, etc., all members
      of the paraffin series. In an extended sense, the term is
      applied to the relation between chemical elements of the
      same group; as, chlorine, bromine, and iodine are said to
      be in homology with each other. Cf. {Heterology}.

   {General homology} (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. --Owen.

   {Serial homology} (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. --Owen. See {Homotypy}.

   {Special homology} (Biol.), the correspondence of a part or
      organ with those of a different animal, as determined by
      relative position and connection. --Owen.