fo·li·um (f ōl e- əm)
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n.pl. fo·li·a(-l e- ə) 1. Geology A thin, leaflike layer or stratum occurring especially in metamorphic rock. 2. Mathematics A plane cubic curve having a single loop, a node, and two ends asymptotic to the same line.
 (click for a larger image) foliumThe equation of the folium of Descartes is x3 + y3 = 3axy. |
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 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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