a. A thin, pliable layer of tissue covering surfaces or separating or connecting regions, structures, or organs of a living organism.
b. A semipermeable layer that bounds a cell or an organelle, typically consisting of lipids and proteins.
2. A thin, pliable sheet or layer of natural or synthetic material: the resonating membrane of a kazoo.
3. A piece of parchment.
4. Chemistry A thin sheet of natural or synthetic material that is permeable to substances in solution.
[Latin membrāna, skin, from membrum, member of the body.]
membra·nal (-brə-nəl) adj.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.