frame of reference

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A set of coordinate axes in terms of which position or movement may be specified or with reference to which physical laws may be mathematically stated.
• noun A set of ideas, as of philosophical or religious doctrine, in terms of which other ideas are interpreted or assigned meaning.

from the GNU version of the Collaborative International Dictionary of English.

• noun an arbitrary set of spatial coordinates used to describe the position or motion of objects. The coordinates may be fixed or moving.
• noun a set of assumptions or conditions that are used to discuss or understand something.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun a set of assumptions, ideas and standards that form a viewpoint from which philosophical, religious and other ideas may be evaluated
• noun physics a set of axes which enable an observer to measure the position and motion of all bodies in some system relative to the reference frame

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a system of assumptions and standards that sanction behavior and give it meaning
• noun a system that uses coordinates to establish position