Viola arvensis vs viola

Viola arvensis and viola both are nouns.

Word	Noun	Adjective	Verb	Adverb
Viola arvensis	Yes	No	No	No
viola	Yes	No	No	No

As nouns, viola is a hypernym of Viola arvensis; that is, viola is a word with a broader meaning than Viola arvensis:

Viola arvensis: common Old World viola with creamy often violet-tinged flowers
viola: any of the numerous plants of the genus Viola

Viola arvensis (noun)	viola (noun)
common Old World viola with creamy often violet-tinged flowers	any of the numerous plants of the genus Viola
	a bowed stringed instrument slightly larger than a violin, tuned a fifth lower