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before vowels prot-, word-forming element meaning "first, source, parent, preceding, earliest form, original, basic," from Greek proto-, comb. form of protos "first," from PIE *pre-, from root *per- (1) "forward, through" (see per).
proto- or prot-
First in time: prototype.
First formed; primitive; original: protoplast.
Having the least amount of a specified element or radical: protoporphyrin.