rivulet vs rill

rivulet and rill both are nouns.

Word	Noun	Adjective	Verb	Adverb
rivulet	Yes	No	No	No
rill	Yes	No	No	No

As nouns, rivulet and rill are synonyms defined as:

Other synonyms of rivulet include run, runnel, streamlet.

rivulet (noun)	rill (noun)
a small stream	a small stream
	a small channel (as one formed by soil erosion)