alteration

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The act or procedure of altering.
• noun The condition resulting from altering; modification.

from The Century Dictionary.

• noun The act of altering; the making of any change; passage from one form or state to another.
• noun A change effected; a change of form or state, especially one which does not affect the identity of the subject.
• noun In mineralogy, the change by which one mineral substance is converted into another, either with or without change of chemical composition; as, for example, the change of the oxid of copper, cuprite, to the carbonate, malachite; or of brookite to rutile, both being forms of titanium dioxid. See paramorphism and pseudomorphism.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of altering or making different.
• noun The state of being altered; a change made in the form or nature of a thing; changed condition.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The act of altering or making different.
• noun The state of being altered; a change made in the form or nature of a thing; changed condition.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the act of revising or altering (involving reconsideration and modification)
• noun the act of making something different (as e.g. the size of a garment)
• noun an event that occurs when something passes from one state or phase to another