Definitions
from The American Heritage® Dictionary of the English Language, 4th Edition
 n. The act or process of equating or of being equated.
 n. The state of being equal.
 n. Mathematics A statement asserting the equality of two expressions, usually written as a linear array of symbols that are separated into left and right sides and joined by an equal sign.
 n. Chemistry A representation of a chemical reaction, usually written as a linear array in which the symbols and quantities of the reactants are separated from those of the products by an equal sign, an arrow, or a set of opposing arrows.
 n. A complex of variable elements or factors: "The world was full of equations . . . there must be an answer for everything, if only you knew how to set forth the questions” ( Anne Tyler).
from Wiktionary, Creative Commons Attribution/ShareAlike License
 n. An assertion that two expressions are equal, expressed by writing the two expressions separated by an equal sign; from which one is to determine a particular quantity.
 n. A small correction to observed values to remove the effects of systematic errors in an observation.
from the GNU version of the Collaborative International Dictionary of English
 n. A making equal; equal division; equality; equilibrium.
 n. An expression of the condition of equality between two algebraic quantities or sets of quantities, the sign = being placed between them
 n. A quantity to be applied in computing the mean place or other element of a celestial body; that is, any one of the several quantities to be added to, or taken from, its position as calculated on the hypothesis of a mean uniform motion, in order to find its true position as resulting from its actual and unequal motion.
from The Century Dictionary and Cyclopedia
 n. A making equal, or an equal division; equality.
 n. In mathematics, a proposition asserting the equality of two quantities, and expressed by the sign = between them; or an expression of the same quantity in two terms dissimilar but of equal value: as, 3 lb. = 48 oz.; x = b + m − r.
 n. In astronomy, the correction or quantity to be added to or subtracted from the mean position of a heavenly body to obtain the true position; also, in a more general sense, the correction arising from any erroneous supposition whatever.
 n. In chem., a collection of symbols used to indicate that two or more definite bodies, simple or compound, having been brought within the sphere of chemical action, a reaction will take place, and new bodies be produced.
 n. An equation for the steady motion of a liquid, namely, where p is the pressure,
ρ the density, V the potential of the impressed forces, q the velocity, and C a constant for each streamline and vortexline, and in the case of irrotational motion a constant for all space.  n. with modern writers, a solution which is a particular case of the general solution;
 n. with older writers, any solution not general. A singular solution is one which is neither general nor implied in the general solution. The complete integral of a partial differential equation is a solution containing the full number of arbitrary constants or functions.
 n. In modern writings, the correction to be applied to the position of a planet or to the time of an eclipse, etc., owing to the finite velocity of light.
 n. In modern astron., the excess of the true over the mean anomaly. (Gauss, Theoria Motus, I. 7.)
 n. The equation of the argument. (Kepler, De Motibus Martis, I. iv.)
 n. Any one of the usual equations of hydrodynamics, where the components of the velocity at fixed points of space are taken as variables: so called in contradistinction to the Lagrangian equations where the coordinates of a definite particle are taken as variables; these equations, though also discovered by Euler, having been used by Lagrauge.
 n. A general equation of hydrodynamics, in which, instead of considering the velocity at each fixed point of space, the motion of each particle is followed out. This is called a Lagrangian equation because used by Lagrange in his “Méchanique Analitique,” though invented by Euler.
 n. An equation of analytical geometry in which certain curves are represented by single letters. Thus, if U = 0, V = 0, W = 0, represent the equations of three circles, UV = W is the symbolic equation of a bicircular quartic
 n.
 n. In the calculus, an equation which contains no differentials.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
 n. the act of regarding as equal
 n. a state of being essentially equal or equivalent; equally balanced
 n. a mathematical statement that two expressions are equal
Etymologies
from Wiktionary, Creative Commons Attribution/ShareAlike License
Examples

But their most brilliant material was deeply mistrustful of words and numbers, like the great "7 x 13 = 28," in which Costello proves the title equation to Abbott in a variety of ways (mostly by ignoring base ten).

I addressed the other half of what you call the equation, that is, the ability to respond. although obviously not to your satisfaction.

Each politician and each issue must be looked at on the particular facts and circumstances, and getting private funds out of the equation is the only way that I can see to remove or temper the tendency or inclination to accommodate private donors.

She will insist that a key component of the equation is the word "involuntary."
Obama's nominee for Office of Legal Counsel: pregnancy is slavery

Complicating the equation is the fact that ticket sales themselves have actually been relatively flat; as a matter of fact, they have shown a slight decline in some recent years.

Whats left out of your equation is the thousands of consumers that benefited, and all the extra resources that opened up for them to do other things with besides pay your guys 17 bucks an hour for a job somebody else can do for 7.

But, her equation is at the level of story: history and fiction tell stories about people, great and small.

In a lot of ways pop seems to be sited more in media where the least important part of the equation is the music.
Freaky Trigger and the Lollards of Pop – Series 3, Week 7  FreakyTrigger

Maybe the problem with the equation is the perceived ‘cost’ of voting.

For forces of the form that Newton studied, such as gravity, the lefthand side of the equation is also invariant.
ruzuzu commented on the word equation
"The equation of time describes the discrepancy between two kinds of solar time. The word equation is used in the medieval sense of "reconcile a difference". The two times that differ are the apparent solar time, which directly tracks the diurnal motion of the Sun, and mean solar time, which tracks a theoretical mean Sun with noons 24 hours apart."
 https://en.wikipedia.org/w/index.php?title=Equation_of_time&oldid=861068135
September 27, 2018