Proto-language is believed to have been a simple language with a limited vocabulary and grammar. It is unlikely that it had a complex grammar like modern languages.

Language evolution, language drift, and language change are all terms used to describe the process by which languages change over time.

All of the above factors can contribute to language change.

Language fusion, language amalgamation, and language blending are all terms used to describe the process by which two or more languages merge into a single language.

Language fission, language division, and language separation are all terms used to describe the process by which a language splits into two or more distinct languages.

All of the above are types of language change.

Semantic change, semantic drift, and semantic shift are all terms used to describe the process by which a word changes its meaning over time.

All of the above are types of semantic change.

Lexical innovation, word formation, and neologism are all terms used to describe the process by which a new word is created.

All of the above are types of lexical innovation.

Compounding, blending, and amalgamation are all terms used to describe the process by which two or more words are combined to form a new word.

Clipping is a type of word formation, not compounding.

Clipping, truncation, and apocope are all terms used to describe the process by which a word is shortened.

Back-formation is a type of word formation, not clipping.

Back-formation, conversion, and zero derivation are all terms used to describe the process by which a new word is created from an existing word by removing the suffix.