slender wild oat vs oat

slender wild oat and oat both are nouns.

Word	Noun	Adjective	Verb	Adverb
slender wild oat	Yes	No	No	No
oat	Yes	No	No	No

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

slender wild oat: oat of southern Europe and southwestern Asia
oat: annual grass of Europe and North Africa; grains used as food and fodder (referred to primarily in the plural: `oats')

slender wild oat (noun)	oat (noun)
oat of southern Europe and southwestern Asia	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')