pin

A pin is a small, slenderfastener or stud, typically made of metal or plastic. Pins are used to hold components together, position parts, or serve as a removable hinge, hinge pin, or alignment aid. Pins come in many forms, ranging from temporary straight pins to permanent retaining pins, and from hardware applications to electronics.

Common mechanical pins include straight pins (dressmaker pins) used in sewing and fabric work; safety pins with a spring-loaded clasp; cotter pins (split pins) used with bolts; dowel pins used for precise alignment; and clevis pins that pass through a hole and are secured. Pin shapes and retention methods vary to suit different loads, materials, and conditions.

Electronic and connector pins refer to the live contacts on connectors or integrated circuit packages. Pins are numbered and arranged in patterns such as dual in-line packages (DIP) or surface-mount packages, and are used to make electrical connections between devices. In many contexts, the term emphasizes both the physical contact point and its electrical function.

PIN code is an acronym for Personal Identification Number, a numeric password used to authenticate a user or card. PINs are widely used in automated teller machines, mobile devices, SIM cards, and secure systems. They are typically four to six digits long and should be kept secret to protect access.

Other uses include bowling, where a pin is one of ten wooden targets arranged for play. In broader language, pin can also be a verb meaning to attach with a pin or to fix something in a particular location or state for tracking or security purposes.