In an *equation*, the quantities on both sides of the equal sign are equal. That's the mathematical meaning of *equation*, but *equation* can also be used in any number of situations, challenges, or efforts to solve a problem.

The "equa" at the beginning of *equation* will be familiar from other words such as "equal," "equality," and "equate." All of these words have to do with making things balance out.
An *equation* is a statement of the equality of two quantities. If that *equation* is not a mathematical one but rather, say, an interpersonal one, it's still a situation in which you might try to make the two sides equal. For example, taking marriage out of the *equation* might make it easier for two people to decide to stay together for a while.