Other forms: equations
An equation is a piece of mathematics with an equals sign in the middle and the same value standing on each side. 2x + 3 = 11 is an equation, and so is E = mc². You solve one by finding the number that makes the two sides balance.
Chemistry keeps its own kind: a chemical equation writes down what goes into a reaction and what comes out, with an arrow where the equals sign would be, and it has to balance too — the same atoms on both sides. Outside science the word is a handy figure of speech for everything bearing on a decision: money is only part of the equation, a baby changes the equation entirely. The related verb is equate, meaning to treat two things as the same, and it takes WITH — he equates being busy with being important. In the middle of equation, the -ti- sounds like the s in vision.
1nounequationA mathematical statement that two expressions have the same value.
“The equation has no solution if the number under the square root is negative.”
2nounchemistryA written account of a chemical reaction, showing what goes in and what comes out.
“Balance the equation so the atoms match on each side.”
3nounwholeThe whole set of factors that bear on a situation.
“Once the children arrived, the whole equation changed.”
Too few real examples of this word to estimate which sense is commonest.
Latin aequātiō meant an equalizing — the act of making two things level. It reached English through Old French, and it is built the plain way: equate plus the ending -ion, the making-equal. That is still exactly what an equation claims, that these two sides weigh the same.
Latin
aequātiō — an equalizing
English, today
equation
From Old French -, from Latin aequātiō (“an equalizing”). Morphologically equate + ion
Etymology from Wiktionary, CC BY-SA