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Related to proto-: Proto-Indo-European
1. First in time; earliest: protolithic.
2. First formed; primitive; original: protohuman.
3. Proto- Being a form of a language that is the ancestor of a language or group of related languages: Proto-Germanic.
4. Having the least amount of a specified element or radical: protoporphyrin.
proto-or sometimes before a vowel
1. indicating the first in time, order, or rank: protomartyr.
2. primitive, ancestral, or original: prototype.
3. (Linguistics) indicating the reconstructed earliest stage of a language: Proto-Germanic.
4. (Chemistry) indicating the first in a series of chemical compounds: protoxide.
5. (Chemistry) indicating the parent of a chemical compound or an element: protactinium.
[from Greek prōtos first, from pro before; see pro-2]
a combining form meaning “first,” “foremost,” “earliest form of” (prototype; protoplasm); used also in the names of chemical compounds that are the first in a given series or that contain the minimum amount of an element. Also, esp. before a vowel,prot-.