zinnia vs white zinnia

zinnia and white zinnia both are nouns.

Word	Noun	Adjective	Verb	Adverb
zinnia	Yes	No	No	No
white zinnia	Yes	No	No	No

As nouns, white zinnia is a hyponym of zinnia; that is, white zinnia is a word with a more specific, narrower meaning than zinnia:

zinnia: any of various plants of the genus Zinnia cultivated for their variously and brightly colored flower heads
white zinnia: subshrub with slender woolly stems and long narrow leaves and flower heads with white rays; southern United States and northern Mexico

Other hyponyms of zinnia include Zinnia acerosa, little golden zinnia, Zinnia grandiflora.

zinnia (noun)	white zinnia (noun)
any of various plants of the genus Zinnia cultivated for their variously and brightly colored flower heads	subshrub with slender woolly stems and long narrow leaves and flower heads with white rays; southern United States and northern Mexico