Avena sativa vs oat

Avena sativa and oat both are nouns.

Word	Noun	Adjective	Verb	Adverb
Avena sativa	Yes	No	No	No
oat	Yes	No	No	No

As nouns, oat is a hypernym of Avena sativa; that is, oat is a word with a broader meaning than Avena sativa:

Avena sativa: widely cultivated in temperate regions for its edible grains
oat: annual grass of Europe and North Africa; grains used as food and fodder (referred to primarily in the plural: `oats')

Avena sativa (noun)	oat (noun)
widely cultivated in temperate regions for its edible grains	seed of the annual grass Avena sativa (spoken of primarily in the plural as `oats')
	annual grass of Europe and North Africa; grains used as food and fodder (referred to primarily in the plural: `oats')