hair drier vs hair dryer

hair drier and hair dryer both are nouns.

Word	Noun	Adjective	Verb	Adverb
hair drier	Yes	No	No	No
hair dryer	Yes	No	No	No

As nouns, hair drier and hair dryer are synonyms defined as:

hair drier and hair dryer: a hand-held electric blower that can blow warm air onto the hair; used for styling hair

Other synonyms of hair drier include blow drier, blow dryer, hand blower.

hair drier (noun)	hair dryer (noun)
a hand-held electric blower that can blow warm air onto the hair; used for styling hair	a hand-held electric blower that can blow warm air onto the hair; used for styling hair