lightening vs whitening

lightening and whitening both are nouns.

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

As nouns, lightening and whitening are synonyms defined as:

lightening (noun)	whitening (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