plectrum

A plectrum (plural: plectra) is held between the thumb and index finger and used to strike individual strings or strum across multiple strings. Modern guitar picks are typically made of nylon, celluloid, or other plastics in various thicknesses — thin picks are flexible and good for strumming, thick picks are rigid and better for single-note playing. Historically, plectra have been made from quill, tortoiseshell, bone, horn, and metal. The harpsichord uses tiny plectra (originally quills, now usually plastic) to pluck its strings mechanically. Mandolin and banjo playing depends entirely on the plectrum, and the tremolo technique on these instruments requires extremely rapid picking.