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homology

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homology

 

  2  definitions  found 
 
  From  Webster's  Revised  Unabridged  Dictionary  (1913)  [web1913]: 
 
  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. 
 
  From  WordNet  r  1.6  [wn]: 
 
  homology 
  n  :  the  quality  of  being  similar  or  corresponding  in  position  or 
  value  or  structure  or  function




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