This article is from the Macintosh application software FAQ, by Elliotte Harold email@example.com with numerous contributions by others.
Once you've used character based styles it's almost impossible
to imagine document formatting without them. After all, just because
you want equations to be formatted in 10 point I Times Italic or
references to menu choices in 12 point Chicago doesn't mean you want
the entire paragraph in that font; but that seems to be the only
choice Word 5.1 and earlier offer. (Word 6 has true character based
styles.) It's truly a shame that a program that makes
working with styles so easy via its ribbon bar and customizable
command key equivalents that can be attached to common styles doesn't
let the user attach styles to less than a paragraph of text at a time.
There is, however, a work-around. Unless you're one of the
fifteen people who actually use color text, you've got six unused
character formats called Blue, Cyan, Green, Magenta, Red, and Yellow
available in the Format Character dialog box and via user-assignable
Command-Keys. (There's also Black and White but using those two will
mess with the normal appearance of your document.) Pick a color for
each different character-based style you want to use and mark your
text with the appropriate color. Then, before saving the document,
do a global Find and Replace for each color; i.e. find the color and
replace with the style attributes like font and font size.