noun (n)

• the act of making something different (as e.g. the size of a garment)(noun.act)

  Synonym:
  adjustment, alteration
  

  source: wordnet30
• slightly modified copy; not an exact copy(noun.artifact)

  Example:
  A modification of last year's model.
  

  source: wordnet30
• the grammatical relation that exists when a word qualifies the meaning of the phrase(noun.linkdef)

  Synonym:
  limiting, qualifying
  

  source: wordnet30
• an event that occurs when something passes from one state or phase to another(noun.event)

  Example:
  The neighborhood had undergone few modifications since his last visit years ago.
  

  Synonym:
  alteration, change
  

  source: wordnet30
• The act of modifying, or the state of being modified; a modified form or condition; state as modified; a change; as, the modification of an opinion, or of a machine; the various modifications of light.(noun)

  source: webster1913