annulus vs fairy circle

annulus and fairy circle both are nouns.

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

As nouns, fairy circle is a hyponym of annulus; that is, fairy circle is a word with a more specific, narrower meaning than annulus:

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

Other hyponyms of annulus include fairy ring.

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