proto-, [Gr. prw^tos first, a superl. fr. pro` before. See Pro-.].
A combining form prefix signifying first, primary, primordial; as, protomartyr, the first martyr; protomorphic, primitive in form; protoplast, a primordial organism; prototype, protozoan. [1913 Webster]
Denoting the first or lowest of a series, or the one having the smallest amount of the element to the name of which it is prefixed; as protoxide, protochloride, etc. [1913 Webster]