n. pl. fo·li·os
a. A large sheet of paper folded once in the middle, making two leaves or four pages of a book or manuscript.
b. A book or manuscript of the largest common size, usually about 38 centimeters (15 inches) in height, consisting of such folded sheets.
a. A leaf of a book numbered only on the front side.
b. A number on such a leaf.
c. A page number.
3. Law A specific number of words used as a unit for measuring the length of the text of a legal document.
tr.v. fo·li·oed, fo·li·o·ing, fo·li·os
To number consecutively the pages or leaves of (a book, for example).
[Middle English, from Late Latin foliō, ablative of folium, leaf of paper, from Latin, leaf; see bhel-3 in the Appendix of Indo-European roots.]
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.