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mole 1 (mōl)
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n.
A skin lesion, commonly a nevus, that is typically raised and discolored.

[Middle English mol, from Old English māl.]

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 
mole 2 (mōl)
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n.
1. Any of various small insectivorous mammals of the family Talpidae of North America and Eurasia, usually living underground and having a thickset body with light brown to dark gray silky fur, strong forefeet for burrowing, and often rudimentary eyes.
2. A machine that bores through hard surfaces, used especially for tunneling through rock.
3. A spy who operates from within an organization, especially a double agent operating against that agent's own government from within its intelligence establishment.

[Middle English molle; akin to possibly akin to MOLD3.]

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 
mole 3 (mōl)
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n.
1. A massive, usually stone wall constructed in the sea, used as a breakwater and built to enclose or protect an anchorage or a harbor.
2. The anchorage or harbor enclosed by a mole.

[French môle, from Italian molo, from Late Greek mōlos, from Latin mōlēs, mass, mole.]

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 
mole 4 (mōl)
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n.
A fleshy abnormal mass formed in the uterus by the degeneration or abortive development of an ovum.

[French môle, from Latin mola, millstone, mole; see melə- in the Appendix of Indo-European roots.]

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 
mole 5 (mōl)
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n. Abbr. mol
Chemistry
In the International System, the base unit used in representing an amount of a substance, equal to the amount of that substance that contains as many atoms, molecules, ions, or other elementary units as the number of atoms in 0.012 kilogram of carbon-12. The number is 6.0221 × 1023, or Avogadro's number. See Table at measurement.

[German Mol, short for Molekulargewicht, molecular weight, from molekular, molecular, from French moléculaire, from molécule, molecule; see MOLECULE.]

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 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:

    Indo-European Roots

    Semitic Roots

    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.

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