Incorrect spelling, explanation: equasion is incorrect because in this case, we should use the suffix -tion, not -sion. These two suffixes are often mistaken, but the reason behind equation being correct is easy to remember. We use the noun suffix -tion when the verb ends with -ate. The verb form of this word is equate, so equation is the correct form.

Correct spelling, explanation: -sion and -tion are commonly mistaken suffixes, which are really two options of the same suffix -ion. There are some rules to when use each of these, and in the case of equation, the reason is pretty simple – one of the rules state that -tion is used with verbs ending with -ate. The verb here is to equate, so equation is the correct form. Moreover, the word comes from French équation, which is from Latin aequationem. As you can see both origins use t not s in spelling. Therefore equation is the correct form and equasion is a mistake.

Definition of equation:
noun, a mathematical statement where two expressions are equal; also: a complicated situation
In the equation 2x – 4 = 20, x equals 12.
The profit here can be calculated with a simple equation.

Collocations with equation:
basic / simple equation
The formula for finding the area of a rectangle is a simple equation.
complex / complicated equation
Solving Einstein’s theory of general relativity involves a complex equation.
solve / work out an equation
I need to work out an equation to calculate the monthly mortgage payment.
equation for
The equation for determining the speed of light is a famous example in physics.
come into an equation
Economic factors such as inflation and interest rates come into an equation when calculating the future value of an investment.

Incorrect spelling

Incorrect spelling