fairy circle vs annulus

fairy circle and annulus both are nouns.

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

As nouns, annulus is a hypernym of fairy circle; that is, annulus 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
annulus: a toroidal shape

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

fairy circle (noun)	annulus (noun)
a ring of fungi marking the periphery of the perennial underground growth of the mycelium	(Fungi) a remnant of the partial veil that in mature mushrooms surrounds the stem like a collar
	a toroidal shape