membrane

American  

[mem-breyn] / ˈmɛm breɪn /

noun

1. Anatomy. a thin, pliable sheet or layer of animal or vegetable tissue, serving to line an organ, connect parts, etc.

2. Cell Biology. the thin, limiting covering of a cell or cell part.

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membrane British  

/ ˈmɛmbreɪn /

noun

1. any thin pliable sheet of material

2. a pliable sheetlike usually fibrous tissue that covers, lines, or connects plant and animal organs or cells

3. biology a double layer of lipid, containing some proteins, that surrounds biological cells and some of their internal structures

4. physics a two-dimensional entity postulated as a fundamental constituent of matter in superstring theories of particle physics

5. a skin of parchment forming part of a roll

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membrane Scientific  

/ mĕm′brān′ /

1. A thin, flexible layer of tissue that covers, lines, separates, or connects cells or parts of an organism. Membranes are usually made of layers of phospholipids containing suspended protein molecules and are permeable to water and fat-soluble substances.

2. See cell membrane

3. Chemistry A thin sheet of natural or synthetic material that is permeable to substances in solution.

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Other Word Forms

• intermembrane adjective
• membraneless adjective

Etymology

Origin of membrane

1375–1425; late Middle English; Middle English membraan parchment < Latin membrāna. See member, -an

Explanation

A membrane is a thin layer of something. For an example of a membrane, you don’t have to look far: your skin is a kind of membrane. Membranes are thin and flexible, but usually still strong enough to protect what’s inside or underneath them. Biologists often study membranes, such as those that surround your cells and organs. There are also membranes that don’t have anything to do with biology. A high-tech jacket might have a waterproof membrane to keep you dry in the rain.

Example Sentences

In addition, internal membrane structures help maintain the separation of nucleoids.

From Science Daily • Apr. 13, 2026

In real viruses, surface proteins are embedded within a lipid membrane and arranged in specific shapes.

From Science Daily • Apr. 12, 2026

This setup mimics the virus's outer membrane, helping preserve the proteins' natural structure and behavior.

From Science Daily • Apr. 12, 2026

The treatment was given as a single injection through a membrane at the base of the cochlea known as the round window.

From Science Daily • Apr. 3, 2026

His cilia are not cilia at all, but individual spirochetes, and at the base of attachment of each spirochete is an oval organelle, embedded in the myxotricha membrane, which is a bacterium.

From "The Lives of a Cell" by Lewis Thomas

Related Words

• sheath
• sheet