If you’ve done any amount of graphic design or typography you’ve no doubt noticed that the apparent size of type varies greatly between fonts when used at the same point size. Some appearing almost double the size of their smaller counterparts.
The reason is that the point size refers to the body that the character occupies, and although type of equal point size may sit on the same body, they will not occupy the space in the same way.
I won’t go into them all, but various elements of the type effect it’s usable size. One of the biggest factors is the x-height, as pictured in this posts heading.
If you were to look at the above two typefaces, Verdana and Goudy Old Style, without the grid lines, it would appear that the Verdana is a larger point size. They are however both 50pt.
As you can seen from the grid lines, the x-height of Verdana is much higher then that of Goudy making the typeface appear larger. This, among other reasons, is why typefaces of equal point sizes appear so different.
Not that this information will help your typography at all, but a little extra knowledge never hurt anyone.
I hope this was interesting.
What other tidbits of information would you like to know?