proto- or prot-
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.
[Greek prōto-, from prōtos; see per1 in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.