cusp vs leaflet

cusp and leaflet both are nouns.

Word	Noun	Adjective	Verb	Adverb
cusp	Yes	No	No	No
leaflet	Yes	No	No	No

As nouns, cusp and leaflet are synonyms defined as:

cusp (noun)	leaflet (noun)
point formed by two intersecting arcs (as from the intrados of a Gothic arch)	a thin triangular flap of a heart valve
small elevation on the grinding surface of a tooth	a small book usually having a paper cover
a thin triangular flap of a heart valve	part of a compound leaf