n. pl. den·si·ties
1. The quality or condition of being dense.
a. The quantity of something per unit measure, especially per unit length, area, or volume.
b. The mass per unit volume of a substance under specified conditions of pressure and temperature.
3. Computers A measure of the number of bits that can be stored in a given amount of physical space on a storage medium.
4. The number of individuals, such as inhabitants or housing units, per unit of area.
5. The degree of optical opacity of a medium or material, as of a photographic negative.
6. Thickness of consistency; impenetrability.
7. Complexity of structure or content.
8. Stupidity; dullness.
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.