The ampersand is the best-known ligature, but there are other common conjoined letters that are less visible. Beyond the five standard Roman ligatures, many type families offer more extensive sets of connected characters. Open Type now makes the use of ligatures effortless, and many fonts offer an array of ligatures. In many Roman typefaces, the lowercase f runs into letters that follow, so Renaissance type foundries solved the problem by creating individual sorts for the five most common problems (ff, fi, fl, ffl and ffi).
Etymology: the Latin verb ligare, to bind, gives us the typographic term ligature for connected letters. Common cognates would be league, ligament, and ligate (to tie off an artery).