degree of freedom

  1. Any of the independent thermodynamic variables, such as pressure, temperature, or composition, required to specify a system with a given number of phases and components.
  2. Any of the independent terms used to characterize the way a physical system can store energy. For example, a molecule consisting of two atoms can be thought of as having three degrees of freedom: one for its linear motion (as the whole molecule moves through space), one for its angular motion (as it rotates around its center of gravity) and one for its internal vibrational energy (as the atoms pull and push against each other within their chemical bond).
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.