ALTER: v.tr. To change or make different; modify: altered my will.  To adjust (a garment) for a better fit. v. intr. To change or become different.
AMEND. v.tr.To change for the better; improve: amended the earlier proposal so as to make it more comprehensive. To remove the faults or errors in; correct. To alter (a legislative measure, for example) formally by adding, deleting, or rephrasing. To enrich (soil), especially by mixing in organic matter or sand. v.intr. To better one's conduct; reform.
CHANGE. To cause to be different: change the spelling of a word.  To give a completely different form or appearance to; transform: changed the yard into a garden.

MODIFY, v.tr. To change in form or character; alter. To make less extreme, severe, or strong: refused to modify her stand on the issue. Grammar. To qualify or limit the meaning of. For example, summer modifies day in the phrase a summer day. v.intr. To be or become modified; change.