### Only one `\``baselineskip` per paragraph

The `\``baselineskip` is not (as one might hope) a property of a line, but of a paragraph. As a result, in a `10pt` (nominal) document (with a default `\``baselineskip` of `12pt`), a single character with a larger size, as:

>     {\Huge A}

will be squashed into the paragraph: TeX will make sure it doesn’t scrape up against the line above, but won’t give it “room to breathe”, as it does the text at standard size; that is, its size (`24.88pt`) is taken account of, but its `\``baselineskip` (`30pt`) isn’t. Similarly

>     Paragraph text ...
>     {\footnotesize Extended interjection ...
>        ... into the paragraph.}
>           ... paragraph continues ...

will look silly, since the `8pt` interjection will end up set on the `12pt` `\``baselineskip` of the paragraph, rather than its preferred `8.5pt`. Finally, something like

>     Paragraph text ...
>       ... paragraph body ends.
>     {\footnotesize Short comment on paragraph.}

>     Next paragraph starts...

will set the body of the first paragraph on the constricted `\``baselineskip` of the `\``footnotesize` comment.

So, how to deal with these problems? The oversized (short) section is typically corrected by a strut: this word comes from movable metal typography, and refers to a spacer that held the boxes (that contained the metal character shapes) apart. Every time you change font size, LaTeX redefines the command `\``strut` to provide the equivalent of a metal-type strut for the size chosen. So for the example above, we would type

>     Paragraph text ...
>        {\Huge A\strut}
>        ... paragraph continues ...

However, more extended insertions (whether of larger or smaller text) are always going to cause problems; while you can strut larger text, ensuring that you strut every line will be tiresome, and there’s no such thing as a “negative strut” that pulls the lines together for smaller text.

The only satisfactory way to deal with an extended insertion at a different size is to set it off as a separate paragraph. A satisfactory route to achieving this is the `quote` environment, which sets its text modestly inset from the enclosing paragraph:

>     Paragraph text ...
>     \begin{quote}
>       \footnotesize This is an inset account
>       of something relevant to the enclosing
>       paragraph...
>     \end{quote}
>     ... paragraph continues ...

Such quote-bracketing also deals with the problem of a trailing comment on the paragraph.

This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=baselinepar