# [Tex/LaTex] Is \baselineskip automatically defined

macros

Is \baselineskip automatically defined by LaTeX? What does it depend on?

I was going through the Wikibook section regarding lengths, and I just realized also that \bigskip and others are not dependent on the font size. Is this the same for baselineskip?

\baselineskip is a tex primitive, so it is always defined to be something (well unless someone goes \let\baselineskip\@undefined but even then the underlying register still has a value even if it is not accessible.
\fontsize{aaa}{bbb}\selectfont

in which case \baselineskip gets set to bbb times the current value of \baselinestretch.