melasma vs mask of pregnancy

melasma and mask of pregnancy both are nouns.

Word	Noun	Adjective	Verb	Adverb
melasma	Yes	No	No	No
mask of pregnancy	Yes	No	No	No

As nouns, melasma and mask of pregnancy are synonyms defined as:

melasma and mask of pregnancy: a tan discoloration of a woman's face that is associated with pregnancy or with the use of oral contraceptives

Other synonyms of melasma include chloasma.

melasma (noun)	mask of pregnancy (noun)
a tan discoloration of a woman's face that is associated with pregnancy or with the use of oral contraceptives	a tan discoloration of a woman's face that is associated with pregnancy or with the use of oral contraceptives