Font sizes can be set with (more or less) absolute commands such as
\LARGE, and so on.
Are there also commands that can increase or reduce a font size by some proportion or percentage not in absolute terms but relative to the preceding text?
I am hoping to find a way to do this in the midst of chapter titles, which are set in the preamble to be
\LARGE\bfseries. But when a colon appears in a chapter title, followed by a subtitle, I am being asked to reduce the size of the subtitle by just a small amount — and the result of using the absolute
\Large is not satisfactory. I could redefine
\Large just for this situation, but I'd prefer to find a relative command to change font size, as described above, as that would be useful in many other situations.