four-o'clock family vs Nyctaginia

four-o'clock family and Nyctaginia both are nouns.

Word	Noun	Adjective	Verb	Adverb
four-o'clock family	Yes	No	No	No
Nyctaginia	Yes	No	No	No

four-o'clock family (noun)	Nyctaginia (noun)
a family of flowering plants of the order Caryophyllales	a caryophyllaceous genus of the family Nyctaginaceae having only one species