lock

A lock is a device used to secure an opening such as a door, container, or cabinet by restricting access. Most mechanical locks rely on a locking mechanism that must be operated by a key, code, or combination. Locks come in many forms, including padlocks, deadbolts, cylinder locks, lever locks, and electronic or smart locks. They are used in homes, businesses, institutions, and public infrastructure.

Most traditional mechanical locks use a key or combination to align internal components and free the bolt to move. In a pin-tumbler lock, for example, correctly cut key lifts pins to create a clear shear line. Other designs use levers, discs, or wafers. Modern electronic locks may rely on codes, RFID, biometrics, or network connectivity.

Lock history: Early mechanical locks appeared in ancient civilizations and were refined in medieval and early modern periods. The development of standardized cylinders and anti-pick features in the 18th and 19th centuries increased security and manufacturing scale.

A canal lock is a chamber with gates that raises or lowers vessels between stretches of water at different elevations. Water is admitted or drained to adjust the chamber level, allowing ships to traverse terrains such as hills and canals.

Lock also refers to a strand of hair, with the plural "locks" used to describe long, flowing hair. The term appears in poetry, fashion, and popular culture.

In computing, a lock is a synchronization primitive that prevents concurrent access to a shared resource, such as a mutex or spinlock. Locks protect against data races in multi-threaded programs.