loosen vs untie

loosen and untie both are verbs.

Word	Noun	Adjective	Verb	Adverb
loosen	No	No	Yes	No
untie	No	No	Yes	No

As verbs, loosen and untie are synonyms defined as:

Other synonyms of loosen include undo.

loosen (verb)	untie (verb)
become loose or looser or less tight	undo the ties of
make loose or looser	cause to become loose
make less dense
disentangle and raise the fibers of
cause to become loose
become less severe or strict
make less severe or strict