indicating the first or earliest or original
"`proto' is a combining form in a word like `protolanguage' that refers to the hypothetical ancestor of another language or group of languages"
Prototypical; preceding the proper beginning of something
"The museum's exhibit features a proto-dinosaur fossil that predates the first true dinosaurs by millions of years."
A surname.
"My neighbor, Mr. Proto, was very helpful when I moved into the new apartment complex."
The word comes from the Greek prefix prōtos, meaning "first." It is used to indicate something that is primary or preliminary.