runnel vs rill

runnel and rill both are nouns.

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

As nouns, runnel and rill are synonyms defined as:

Other synonyms of runnel include rivulet, run, streamlet.

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