cost overrun vs cost

cost overrun and cost both are nouns.

Word	Noun	Adjective	Verb	Adverb
cost overrun	Yes	No	No	No
cost	Yes	No	Yes	No

As nouns, cost is a hypernym of cost overrun; that is, cost is a word with a broader meaning than cost overrun:

cost overrun: excess of cost over budget
cost: the total spent for goods or services including money and time and labor

cost overrun (noun)	cost (noun)
excess of cost over budget	the property of having material worth (often indicated by the amount of money something would bring if sold)
	value measured by what must be given or done or undergone to obtain something
	the total spent for goods or services including money and time and labor

cost overrun (verb)	cost (verb)
	be priced at
	require to lose, suffer, or sacrifice