graphite vs pencil lead

graphite and pencil lead both are nouns.

Word	Noun	Adjective	Verb	Adverb
graphite	Yes	No	No	No
pencil lead	Yes	No	No	No

As nouns, pencil lead is a hyponym of graphite; that is, pencil lead is a word with a more specific, narrower meaning than graphite:

graphite: used as a lubricant and as a moderator in nuclear reactors
pencil lead: mixture of graphite with clay in different degrees of hardness; the marking substance in a pencil

Other hyponyms of graphite include lead, pencil.

graphite (noun)	pencil lead (noun)
used as a lubricant and as a moderator in nuclear reactors	mixture of graphite with clay in different degrees of hardness; the marking substance in a pencil