round shape vs ringlet

round shape and ringlet both are nouns.

Word	Noun	Adjective	Verb	Adverb
round shape	Yes	No	No	No
ringlet	Yes	No	No	No

As nouns, ringlet is a hyponym of round shape; that is, ringlet is a word with a more specific, narrower meaning than round shape:

round shape: a shape that is curved and without sharp angles
ringlet: a round shape formed by a series of concentric circles (as formed by leaves or flower petals)

round shape (noun)	ringlet (noun)
a shape that is curved and without sharp angles	any of various butterflies belonging to the family Satyridae
	a little ring
	lock of hair in the shape of a spiral or curl
	a round shape formed by a series of concentric circles (as formed by leaves or flower petals)