linear equation

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

• noun An algebraic equation, such as y = 2x + 7 or 3x + 2y − z = 4, in which the highest degree term in the variable or variables is of the first degree. The graph of such an equation is a straight line if there are two variables.

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

• noun mathematics A polynomial equation of the first degree (such as x = 2y - 7)

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

• noun a polynomial equation of the first degree