For example, in the letter y, the descender is the "tail", or that portion of the diagonal line which lies below the v created by the two lines converging. In the letter p, it is the stem reaching down past the o.
In most fonts, descenders are reserved for lowercase characters such as g, j, q, p, y, and sometimes f. Some fonts, however, also use descenders for some numerals (typically 3, 4, 5, 7, and 9). Such numerals are called old-style numerals. (Some italic fonts, such as Computer Modern italic, put a descender on the numeral 4 but not on any other numerals. Such fonts are not considered old-style.) Some fonts also use descenders for the tails on a few uppercase letters such as J and Q.
Descenders are often reduced in small-print typefaces for uses such as newspapers, directories or pocket Bibles to fit more text on a page. More radically, on 20 May 1802 Philip Rusher of Banbury patented a new Patent Type with eliminated descenders and shortened ascenders. The type did not prove successful, nor did another use in 1852. The Art Noveau display typeface Hobo and headline typeface Permanent Headline which also eliminate descenders have both been somewhat popular since.