A plectrum (plural: plectra) is a device for plucking or strumming a stringed instrument. In guitars, banjos, and similar instruments, the plectrum is a separate tool held in the player's hand. In harpsichords, the plectra form part of the mechanism of the instrument.

Plectra for guitars, etc.

A plectrum for guitars, etc., typically takes the form of a narrow isosceles triangle with rounded corners; the acutest angle is the one commonly used to pluck the string. Such a plectrum can also be called a pick (or a flatpick to distinguish it from finger picks). They are made of a variety of materials, plastic being the most common. The size, shape and thickness may vary considerably. Items such as small coins may successfully be used as a substitute plectrum if the need arises.

Banjo and guitar players may wear a thumb pick mounted on a ring, and sometimes finger picks on their fingertips.

Plectra for harpsichords

In a harpsichord, the plectra (one for each string) are very small, often only about a centimeter long, about 1.5 millimeters wide, and perhaps half a millimeter thick. The plectrum is gently tapered, being narrowest at the plucking end. The top surface of the plectrum is flat and horizontal, and is held in the tongue of the jack, which permits it to pluck moving upward and pass almostly silently past the string moving downward.

Historically, plectra were made of sturdy quills (that is, large feathers). Crow quills were considered best, followed by raven quills. In some Italian harpsichords, leather plectra were used. In late French harpsichords by the great builder Pascal Taskin, peau de buffle, a chamois-like material from the hide of the European buffalo, was used for plectra that produced a delicate pianissimo. Of these materials, quill was by far the most common.

Modern harpsichords often substitute a more durable plastic, such as delrin, for quill; thus modern harpsichordists need not spend much of their time, as J. S. Bach did, requilling their instruments.