A pencil is a writing implement or art medium usually constructed of a narrow, solid pigment core inside a protective casing. The case prevents the core from breaking, and also from marking the user’s hand during use.

Pencils create marks via physical abrasion, leaving behind a trail of solid core material that adheres to a sheet of paper or other surface. They are noticeably distinct from pens, which dispense liquid or gel ink that stain the light colour of the paper.

Most pencil cores are made of graphite mixed with a clay binder, leaving grey or black marks that can be easily erased. Graphite pencils are used for both writing and drawing, and the result is durable: although writing can usually be removed with an eraser, it is resistant to moisture, most chemicals, ultraviolet radiation and natural aging. Other types of pencil core are less widely used. Charcoal pencils are mainly used by artists for drawing and sketching.

Coloured pencils are sometimes used by teachers or editors to correct submitted texts but are more usually regarded as art supplies, especially those with waxy core binders that tend to smear on paper instead of erasing. Grease pencils have a softer crayon-like waxy core that can leave marks on smooth surfaces such as glass or porcelain.

The most common type of pencil casing is a thin wooden cylinder permanently bonded around the core. Similar permanent casings may be constructed of other materials such as plastic or paper. To use the pencil, the casing must be carved or peeled off to expose the working end of the core as a sharp point.

Mechanical pencils have more elaborate casings that support mobile pieces of pigment core, which can be extended or retracted through the casing tip as needed.