The vertical proportions are also very important for the look of the alphabet; They influence economy, readability at a given size, and, indirectly, the x-height: a 12pt character is 12 points from ascender to descender — the longer they are, the less space is available for the x-Height.
The ascender is, as seen in the illustration, not necessarily the same as the cap height.
The ascender is measured from the baseline and expressed here in relation to the x-Height.