roughage vs bran

roughage and bran both are nouns.

Word	Noun	Adjective	Verb	Adverb
roughage	Yes	No	No	No
bran	Yes	No	No	No

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

roughage: coarse, indigestible plant food low in nutrients; its bulk stimulates intestinal peristalsis
bran: food prepared from the husks of cereal grains

roughage (noun)	bran (noun)
coarse, indigestible plant food low in nutrients; its bulk stimulates intestinal peristalsis	food prepared from the husks of cereal grains
	broken husks of the seeds of cereal grains that are separated from the flour by sifting