PIE-- the largest and most diverse offshoot from Proto-World. As there are a lot of people who don't know linguistics, I was being very facetious there. "Proto-World," the idea that all language share an ancestor, is a very naive theory that has next to no supporting evidence. And Indo-European languages are certainly not the most diverse language family- even though they might be the most widely spoken, both in terms of area and population. This description is falling apart. Okay

Sources:
https://alic.sites.unlv.edu/chapter-1...
https://lrc.la.utexas.edu/books/piep/...
https://ahdictionary.com/word/indoeur...
https://www.ling.upenn.edu/~kroch/cou...
https://www.ling.upenn.edu/~rnoyer/co...
https://gucorpling.org/amir/IE_Glossa...

0:00 Introduction
0:41 Phonology
4:10 Vowels and Ablaut
5:42 Ablaut example
6:52 Roots vs. Words
7:22 Lexemes vs. Words
7:57 Verb Inflection
9:16 Noun Inflection
11:31 Example Sentence