spearhead vs spear

spearhead and spear both are nouns.

Word	Noun	Adjective	Verb	Adverb
spearhead	Yes	No	Yes	No
spear	Yes	No	Yes	No

spearhead (noun)	spear (noun)
the head and sharpened point of a spear	a long pointed rod used as a tool or weapon
the leading military unit in an attack	an implement with a shaft and barbed point used for catching fish
someone who leads or initiates an activity (attack or campaign etc.)

spearhead (verb)	spear (verb)
be the leader of	pierce with a spear
	thrust up like a spear