Yes, Matlab is case sensitive.  Also, by convention, all built-in functions are lower case.

However, confusingly, Matlab’s documentation uniformly describes them using upper case.  Fortunately, that isn’t so bad once you realize that all Matlab documentation is incorrect in this way, it only trips you up at first.

You may use lower, upper, or mixed case for your own variables and functions but lower case is preferred for function names since it allows you to document them in upper case, per Matlab’s convention. (We assume that the best way to dispel confusion is to perpetuate it.)