In this subthread, the phrase "0-based / 1-based" is for the word "base" accessing the first element which is semantically equivalent to x[0] in C/C++/Python/e

In this subthread, the phrase "0-based / 1-based" is for the word "base" accessing the first element which is semantically equivalent to x[0] in C/C++/Python/etc or x[1] in R Language. Yes in Mathematica, putting "0" between "[" "]" will get you the reserved "head" but that's not how people are talking about "0-based" here.