certain vs positive

certain is not a noun while positive is a noun.

Word	Noun	Adjective	Verb	Adverb
certain	No	Yes	No	No
positive	Yes	Yes	No	No

certain (noun)	positive (noun)
	a film showing a photographic image whose tones correspond to those of the original subject
	the primary form of an adjective or adverb; denotes a quality without qualification, comparison, or relation to increase or diminution

certain (adjective)	positive (adjective)
established beyond doubt or question; definitely known	characterized by or displaying affirmation or acceptance or certainty etc.
having or feeling no doubt or uncertainty; confident and assured	indicating existence or presence of a suspected condition or pathogen
certain to occur; destined or inevitable	reckoned, situated or tending in the direction which naturally or arbitrarily is taken to indicate increase or progress or onward motion
established irrevocably	of or relating to positivism
exercising or taking care great enough to bring assurance	involving advantage or good
definite but not specified or identified	persuaded of; very sure
reliable in operation or effect	having a positive charge
	marked by excessive confidence
	formally laid down or imposed
	greater than zero
	impossible to deny or disprove