Here is a response from our resident linguist, Jacque Russom:

     ... here is the long-winded linguist's answer:

     Homonym -- a word that "sounds" the same as another word (him,
         hymn)

     Synonym -- a word that "means" the same as another word (dog,
         canine)

     Hypernym -- a word that is the category name of other words (tree
         is the hypernym of ash, elm, birch, beech, oak)

     Hyponym -- a word that is in the category named by the hypernym
         (oak is a hyponym of tree)