camelia vs japonica

camelia and japonica both are nouns.

Word	Noun	Adjective	Verb	Adverb
camelia	Yes	No	No	No
japonica	Yes	No	No	No

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

camelia: any of several shrubs or small evergreen trees having solitary white or pink or reddish flowers
japonica: greenhouse shrub with glossy green leaves and showy fragrant rose-like flowers; cultivated in many varieties

Other hyponyms of camelia include Camellia japonica.

camelia (noun)	japonica (noun)
any of several shrubs or small evergreen trees having solitary white or pink or reddish flowers	deciduous thorny shrub native to Japan having red blossoms
	greenhouse shrub with glossy green leaves and showy fragrant rose-like flowers; cultivated in many varieties