a. A line segment that joins the origin and a variable point in a system of polar or spherical coordinates.
b. The length of such a line segment.
2. Astronomy A straight line connecting the center of mass of a satellite, such as a planet, moon, or comet, to the center of mass of the body it orbits, such as the sun or Earth. Also called position vector.
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.