an act or instance of modifying.

the state of being modified; partial alteration.

a modified form; variety.

Biology . a change in a living organism acquired from its own activity or environment and not transmitted to its descendants.

limitation or qualification.

Grammar .

the use of a modifier in a construction, or of modifiers in a class of constructions or in a language.

the meaning of a modifier, esp. as it affects the meaning of the word or other form modified

Limitation is one kind of modification.

a change in the phonological shape of a morpheme, word, or other form when it functions as an element in a construction, as the change of not to -n't in doesn't.

an adjustment in the form of a word as it passes from one language to another.

noun

alteration , mutation , permutation , variation