What do a.m. and p.m. stand for?


[mem-breyn] /ˈmɛm breɪn/
Anatomy. a thin, pliable sheet or layer of animal or vegetable tissue, serving to line an organ, connect parts, etc.
Cell Biology. the thin, limiting covering of a cell or cell part.
Origin of membrane
late Middle English
1375-1425; late Middle English; Middle English membraan parchment < Latin membrāna. See member, -an
Related forms
membraneless, adjective
intermembrane, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for membrane
  • Their secret is a patented three-layer membrane that lets perspiration out for comfort but prevents all moisture from penetrating.
  • In reverse osmosis, also known as ultrafiltration, the wine flows along a porous cylindrical membrane.
  • Almost a third of these are embedded in the cell's outer membrane.
  • On this day, the fishermen debate which is tastier, mullet roe fried intact in its membrane or chopped and scrambled with eggs.
  • These attract the calcite particles, which build up on the membrane in crisp, geometric columns until they make a shell.
  • Most drugs and diseases target these membrane proteins, so knowing their shape is important.
  • Snell's theory of the lung membrane had to do with the limits of oxygen.
  • The membrane is impermeable to blood cells and large molecules such as proteins, but small ones can get through it.
  • In all other mammals, the lungs are surrounded by two layers of a thin membrane called the pleural cavity.
  • The optical properties of the fibre then vary depending on the pressure differential across the membrane.
British Dictionary definitions for membrane


any thin pliable sheet of material
a pliable sheetlike usually fibrous tissue that covers, lines, or connects plant and animal organs or cells
(biology) a double layer of lipid, containing some proteins, that surrounds biological cells and some of their internal structures
(physics) a two-dimensional entity postulated as a fundamental constituent of matter in superstring theories of particle physics
a skin of parchment forming part of a roll
Word Origin
C16: from Latin membrāna skin covering a part of the body, from membrummember
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for membrane

early 15c., "thin layer of skin or tissue," a term in anatomy, from Latin membrana "a skin, membrane; parchment (skin prepared for writing)," from membrum "limb, member of the body" (see member). The etymological sense is "that which covers the members of the body."

Online Etymology Dictionary, © 2010 Douglas Harper
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membrane in Medicine

membrane mem·brane (měm'brān')

  1. A thin pliable layer of tissue covering surfaces, enveloping a part, lining a cavity, or separating or connecting structures or organs.

  2. Cell membrane.

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

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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membrane in Science
  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.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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