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clé is a feminine French noun meaning "key." The singular form is clé, the plural clés. Modern usage favors the acute-accented spelling clé; clef is a historical variant that remains in fixed expressions or older texts. The word derives from Latin clavis, meaning a device that opens a lock, and has extended to many other senses in French.

In everyday language, clé refers to a physical key used to operate locks or containers, such as a door key, a mailbox key, or a key to a car. It also appears in numerous compound terms for tools and devices, such as clé Allen (Allen wrench) or clé USB (USB flash drive). Metaphorically, clé is used to denote something essential or decisive, for example “la clé du problème” (the key to the problem).

In technology and information security, the word forms part of specialized phrases: clé publique and clé privée (public key and private key) in public-key cryptography; clé secrète or clé symétrique for symmetric keys; and clé d’activation or clé produit for software activation codes. In databases, clé primaire refers to a primary key, and clé étrangère to a foreign key.

In music notation, clé (also historically clef) designates the clef, the symbol placed at the beginning of a staff to indicate the pitch range. Common examples are clé de sol (treble clef) and clé de fa (bass clef). While the English term “clef” survives in some musical contexts, French usage overwhelmingly employs clé.