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 the Americas, doctors can help infected people by putting them on a life-support machine known as ECMO, for extracorporeal membrane oxygenation, which breathes for the patient by oxygenating the blood.

From Los Angeles Times • May 4, 2026

In cases where hantavirus infection is suspected, Mertz said people should seek out urban medical centers that offer extracorporeal membrane oxygenation, which can be used to support the lungs.

From MarketWatch • May 4, 2026

This behavior highlights the role of membrane chemistry.

From Science Daily • Apr. 29, 2026

Ras inhibitors block a small protein that sits inside the cell membrane and acts as an on/off switch, setting off a signaling cascade that can make a cell grow or divide.

From Barron's • Apr. 28, 2026

The cell was a beaker of chemicals, biochemists argued, a pouch of compounds bound by a membrane that were reacting to produce a phenomenon called “life.”

From "The Gene" by Siddhartha Mukherjee

Related Words

• sheath
• sheet