Lagrangian point definition by American Heritage Dictionary
The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Astronomy Any of five points, stable with respect to gravitational forces and in the orbital plane of two bodies, one of which is much larger than the other. A third, smaller body placed at one of these points will remain in equilibrium with respect to the other two bodies.
Origin: After Comte Joseph Louis Lagrange.
lagrangian point - Science Definition
A point in space where a small body with negligible mass under the gravitational influence of two large bodies will remain at rest relative to the larger ones. In a system consisting of two large bodies (such as the Sun-Earth system or the Moon-Earth system), there are five Lagrangian points (L1 through L5). Knowledge of these points is useful in deciding where to position orbiting bodies.