1. Mathematics A three-dimensional surface, all points of which are equidistant from a fixed point.
2. A spherical object or figure.
3. A celestial body, such as a planet or star.
4. The sky, appearing as a hemisphere to an observer: the sphere of the heavens.
5. Any of a series of concentric, transparent, revolving globes that together were once thought to contain the moon, sun, planets, and stars.
a. A range or extent of knowledge, interest, or activity: a problem that falls within the sphere of biophysics. See Synonyms at field.
b. A social level or part of society or group: knew few people beyond his partner's sphere.
c. A range of power or influence: within the sphere of the empire.
tr.v. sphered, spher·ing, spheres
1. To form into a sphere.
2. To put in or within a sphere.
[Middle English spere, from Old French espere, from Latin sphaera, from Greek sphaira.]
sphe·rici·ty (sfîr-ĭsĭ-tē) n.
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.