fixed cost vs fixed costs

fixed cost and fixed costs both are nouns.

Word	Noun	Adjective	Verb	Adverb
fixed cost	Yes	No	No	No
fixed costs	Yes	No	No	No

As nouns, fixed cost and fixed costs are synonyms defined as:

fixed cost and fixed costs: a periodic charge that does not vary with business volume (as insurance or rent or mortgage payments etc.)

Other synonyms of fixed cost include fixed charge.

fixed cost (noun)	fixed costs (noun)
a periodic charge that does not vary with business volume (as insurance or rent or mortgage payments etc.)	a periodic charge that does not vary with business volume (as insurance or rent or mortgage payments etc.)