loosening vs modification

loosening and modification both are nouns.

Word	Noun	Adjective	Verb	Adverb
loosening	Yes	No	No	No
modification	Yes	No	No	No

As nouns, modification is a hypernym of loosening; that is, modification is a word with a broader meaning than loosening:

loosening: the act of making something less tight
modification: the act of making something different (as e.g. the size of a garment)

Other hypernyms of loosening include adjustment, alteration.

loosening (noun)	modification (noun)
the act of making something less tight	the act of making something different (as e.g. the size of a garment)
an occurrence of control or strength weakening	slightly modified copy; not an exact copy
	an event that occurs when something passes from one state or phase to another
	the grammatical relation that exists when a word qualifies the meaning of the phrase