pellet vs BB

pellet and BB both are nouns.

Word	Noun	Adjective	Verb	Adverb
pellet	Yes	No	No	No
BB	Yes	No	No	No

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

Other hyponyms of pellet include BB shot, bird shot, buckshot, duck shot, grape, grapeshot, ball, musket ball.

pellet (noun)	BB (noun)
a solid missile discharged from a firearm	a small pellet fired from an air rifle or BB gun
a small rounded mass of a substance