whitening vs lightening

whitening and lightening both are nouns.

Word	Noun	Adjective	Verb	Adverb
whitening	Yes	No	No	No
lightening	Yes	No	No	No

As nouns, whitening and lightening are synonyms defined as:

whitening (noun)	lightening (noun)
changing to a lighter color	changing to a lighter color
	descent of the uterus into the pelvic cavity that occurs late in pregnancy; the fetus is said to have dropped