This atlas traces the Latin R's sound back to Phoenician resh, meaning head, through Greek rho elsewhere. Rho in classical Greek is written as a simple bow on a vertical stroke, visually identical to a Roman P, since both letters share that same Phoenician ancestor and occupy the same alphabetic position; the resemblance is close enough that unwary readers of Greek inscriptions sometimes mistake rho for a Latin P at a glance.
Etruscan and Roman scribes, working with an alphabet that already contained a letter shaped exactly like rho for the unrelated sound of P, added a short diagonal leg to the bow to create a graphically distinct letter for their own /r/ sound, producing the Roman capital R still used today. That added leg is R's single defining graphic feature, and it has remained stable since the classical period; the lowercase r, formed in medieval cursive by simplifying the bow into a small hook while keeping a short diagonal stroke, is one of the more variable lowercase forms across typefaces, some retaining a full bow and others reducing it nearly to a single stroke. Medieval scribes also used a separate, compressed rotunda form of r, resembling a numeral 2, after letters ending in a curve such as o or b, a space-saving convention common in manuscript and early printed books that has no equivalent among the surrounding letters and disappeared from ordinary typesetting by the close of the hand-press era.