How to change type size used for footnotes in LaTeX

Footnotes in a LaTeX document are rendered in the predefined footnotesize type size. This size lies between the scriptsize and small of the 9 type sizes in LaTeX. The size of footnotes in a LaTeX document can be changed by setting it one of the other 8 type sizes of LaTeX.

For example, to reduce the footnote type size by one increment:

\renewcommand{\footnotesize}{\scriptsize}