signal flag vs pennant

signal flag and pennant both are nouns.

Word	Noun	Adjective	Verb	Adverb
signal flag	Yes	No	No	No
pennant	Yes	No	No	No

As nouns, pennant is a hyponym of signal flag; that is, pennant is a word with a more specific, narrower meaning than signal flag:

Other hyponyms of signal flag include code flag, nautical signal flag, red flag.

signal flag (noun)	pennant (noun)
a rectangular piece of fabric used as a signalling device	a long flag; often tapering
	a flag longer than it is wide (and often tapering)
	the award given to the champion