English Reference
noun

sheath

n.
US /ˈʃiθ/ UK /ʃˈiːθ/ sheath UK spelling sheathed, sheaths

  1. 01 B2 Upper Intermediate

    a protective case for a sword, knife, or other sharp blade.

    a close-fitting cover for a blade, traditionally made of leather or metal.

    Simple

    The hunter slid his knife back into its leather sheath after cleaning the fish.

    In context

    The ceremonial sword was housed in a gold-plated sheath, intricately engraved with scenes from the kingdom's history.

    scabbardcaseholster
  2. 02 C1 Advanced Technical Technical

    the outer layer of plastic or rubber that protects an electrical wire.

    the protective outer covering of an electrical cable or wire, providing insulation and mechanical protection.

    Simple

    The electrician noticed that the plastic sheath of the wire was cracked.

    In context

    Heavy-duty industrial cables require a reinforced sheath to withstand the extreme temperatures and friction of the factory floor.

  3. 03 B2 Upper Intermediate

    a type of tight-fitting dress that follows the shape of a woman's body.

    a close-fitting, straight-cut dress, often sleeveless and typically ending near the knee.

    Simple

    She wore a simple black sheath dress to the cocktail party.

    In context

    The designer's spring collection featured silk sheath dresses that emphasised a minimalist silhouette through precise tailoring.

    shift dress
  4. 04 C1 Advanced Technical Science

    a natural covering on a plant or animal, like the base of a leaf on a stem.

    an enveloping tubular structure, such as the base of a grass leaf or a protective membrane in animal anatomy.

    Simple

    In many types of grass, the leaf forms a sheath around the stem.

    In context

    The nerve fibres are protected by a myelin sheath, which is essential for the rapid transmission of electrical impulses.

  5. 05 C1 Advanced British EnglishInformal Medicine

    a rubber cover used during sex for protection.

    a contraceptive device worn over the penis.

    Simple

    The clinic provides free sheaths and health advice to young adults.

    In context

    Public health campaigns in the 1980s often used the term sheath as a more formal or clinical alternative to common slang.

    Teacher's tip

    This term is somewhat dated or clinical in many regions; 'condom' is the standard term used in modern English.

    condomprophylactic

In adult brains, the researchers detected changes in myelination that could be traced to thicker myelin sheaths, particularly around thin axons.

ScienceDaily· 14 Aug 2026

Etymology 1

From Middle English sheth, shethe (“holder for a sword, knife, etc., scabbard, sheath”) [and other forms], from Old English sċēaþ (“sheath”), from Proto-West Germanic skaiþiju, from Proto-Germanic skaiþiz (“sheath; covering”), from Proto-Indo-European *skey- (“to dissect, split”) (possibly from the notion of a split stick with a sword inserted). The English word is cognate with Danish skede, Dutch schede, Icelandic skeið, German Scheide, Low German scheed, Norwegian skjede.

Etymology 2

A variant of sheathe.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin ine-pro *skey-
Level C1 · Advanced
Frequency Occasional
Updated