four o'clock vs flower

four o'clock and flower both are nouns.

Word	Noun	Adjective	Verb	Adverb
four o'clock	Yes	No	No	No
flower	Yes	No	Yes	No

As nouns, flower is a hypernym of four o'clock; that is, flower is a word with a broader meaning than four o'clock:

four o'clock: any of several plants of the genus Mirabilis having flowers that open in late afternoon
flower: a plant cultivated for its blooms or blossoms

four o'clock (noun)	flower (noun)
any of several plants of the genus Mirabilis having flowers that open in late afternoon	a plant cultivated for its blooms or blossoms
	reproductive organ of angiosperm plants especially one having showy or colorful parts
	the period of greatest prosperity or productivity

four o'clock (verb)	flower (verb)
	produce or yield flowers