flag vs pennant

flag and pennant both are nouns.

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

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

flag: emblem usually consisting of a rectangular piece of cloth of distinctive design
pennant: a long flag; often tapering

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

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

flag (noun)	pennant (noun)
a conspicuously marked or shaped tail	a long flag; often tapering
emblem usually consisting of a rectangular piece of cloth of distinctive design	a flag longer than it is wide (and often tapering)
stratified stone that splits into pieces suitable as paving stones	the award given to the champion
flagpole used to mark the position of the hole on a golf green
a rectangular piece of fabric used as a signalling device
a listing printed in all issues of a newspaper or magazine (usually on the editorial page) that gives the name of the publication and the names of the editorial staff, etc.
plants with sword-shaped leaves and erect stalks bearing bright-colored flowers composed of three petals and three drooping sepals

flag (verb)	pennant (verb)
provide with a flag
become less intense
communicate or signal with a flag
decorate with flags
droop, sink, or settle from or as if from pressure or loss of tautness