Amelioration

             Change to a more favorable meaning

Pejoration

                  Change to a more negative meaning

Strengthening

          Intensification of meaning (relatively rare)

Weakening

      Diluting of meaning

     Occurs when a specific, concrete meaning changes to a more abstract meaning.  

Concretization

Change in meaning from abstract to specific and concrete

Generalization

Extention of meaning to cover wider semantic areas

Narrowing

(more common than generalization) 

        Restriction in the range of meaning(s) of a word

Shift in Denotation

Occurs when the real-world reference of a word changes

   ie. OE clud meant "rock,hill," and PDE descedant is cloud.

Shift in Connotation

 Similar to amelioration and pejoration, but not necessarily confined to simply positive vs. neative.  Instead, refers to the entire set of associations that one makes to a word in addition to its denotative or literal sense.  

ie. OE Wyrm "dragon, serpent, snake" PDE worm