An ascender is the part of a lower-case letter that extends above the x-line to near the height of a capital letter. Examples of this are the letters b, d, f, h, k, and l. The level to which ascenders reach is called the ascent line, which may or may not technically correspond to the cap height in a given font. Capital letters do not conventionally possess ascenders.
The ascender of the letter f—or at least a portion of it—may also be called a hook or occasionally an arch. In some typefaces, the other letters with ascenders may exhibit a hook as well, reflecting their handwritten or cursive forms. The serifs that cap the top of vertical ascenders (in serif fonts ) are called a unilateral serifs in that they are one-sided, and head serifs in that they are located at the top of the strokes.