Ascender - The part of a lowercase letters, b, d, f, h, k, l, and t that rises above the x-height.
Ascender line - Defines the height of lowercase ascenders (often, but not always, the same as the cap line).
Base line - Defines the bottom of capital letters and of lowercase letters (excluding descenders).
Descender - The part of lowercase letters, g, j, p, q, and y, that falls below the baseline.
Descender line - Defines the depth of lowercase descenders.
X-Height - The height of lowercase letters excluding ascenders and descenders.