fairy circle vs doughnut

fairy circle and doughnut both are nouns.

Word	Noun	Adjective	Verb	Adverb
fairy circle	Yes	No	No	No
doughnut	Yes	No	No	No

As nouns, doughnut is a hypernym of fairy circle; that is, doughnut is a word with a broader meaning than fairy circle:

fairy circle: a ring of fungi marking the periphery of the perennial underground growth of the mycelium
doughnut: a toroidal shape

Other hypernyms of fairy circle include anchor ring, annulus, halo, ring.

fairy circle (noun)	doughnut (noun)
a ring of fungi marking the periphery of the perennial underground growth of the mycelium	a small ring-shaped friedcake
	a toroidal shape