1. 
   Covariation
   Phenomenon observed in aligned homologous sequence sets wherein side chains at different sequence positions have apparently changed synchronously
   Found op http://www.encyclo.co.uk/visitor-contributions.php
   
   
2. 
   covariation
   noun (statistics) correlated variation
   Found op http://wordnetweb.princeton.edu/perl/webwn?s=covariation
   
   

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