seborrheic eczema vs dermatitis

seborrheic eczema and dermatitis both are nouns.

Word	Noun	Adjective	Verb	Adverb
seborrheic eczema	Yes	No	No	No
dermatitis	Yes	No	No	No

As nouns, dermatitis is a hypernym of seborrheic eczema; that is, dermatitis is a word with a broader meaning than seborrheic eczema:

seborrheic eczema: a chronic skin disease associated with seborrhea and greasy scales on the scalp or eyelids or other parts of the skin
dermatitis: inflammation of the skin; skin becomes itchy and may develop blisters

seborrheic eczema (noun)	dermatitis (noun)
a chronic skin disease associated with seborrhea and greasy scales on the scalp or eyelids or other parts of the skin	inflammation of the skin; skin becomes itchy and may develop blisters