biquadratic equation vs biquadratic

biquadratic equation and biquadratic both are nouns.

Word	Noun	Adjective	Verb	Adverb
biquadratic equation	Yes	No	No	No
biquadratic	Yes	Yes	No	No

As nouns, biquadratic equation and biquadratic are synonyms defined as:

biquadratic equation (noun)	biquadratic (noun)
an equation of the fourth degree	a polynomial of the fourth degree
	an equation of the fourth degree
	an algebraic equation or function of the fourth degree

biquadratic equation (adjective)	biquadratic (adjective)
	involving the fourth and no higher power of a quantity or degree