v. mod·u·lat·ed, mod·u·lat·ing, mod·u·lates
1. To regulate or adjust to a certain degree: physiological mechanisms that modulate the body's metabolic rate.
2. To change or vary the pitch, intensity, or tone of (one's voice or a musical instrument, for example).
a. To vary the frequency, amplitude, phase, or other characteristic of (electromagnetic waves).
b. To vary (electron velocity) in an electron beam.
4. Biochemistry To act on (a receptor, for example) as an activator, an inhibitor, or both.
To move from one key or tonality to another by means of a melody or chord progression.
[Latin modulārī, modulāt-, to measure off, to regulate, from modulus, diminutive of modus, measure; see med- in the Appendix of Indo-European roots.]
modu·la′tive, modu·la·to′ry (-lə-tôr′ē) adj.
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:
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.