pennon vs streamer

pennon and streamer both are nouns.

Word	Noun	Adjective	Verb	Adverb
pennon	Yes	No	No	No
streamer	Yes	No	No	No

As nouns, pennon and streamer are synonyms defined as:

Other synonyms of pennon include pennant, waft.

pennon (noun)	streamer (noun)
wing of a bird	long strip of cloth or paper used for decoration or advertising
a long flag; often tapering	a long flag; often tapering
	a newspaper headline that runs across the full page
	light that streams