Is A Circle A Function? Grasping Mathematical Concepts

Is A Circle A Function

Maths is all around us, and we do a lot of mathematical calculations during the day to get through various processes without knowing it.

Without taking a step back to look at them, we would never know how these calculations are important to our daily lives.

You can cut the calculations down to equations, formulas, and functions, which are integral to mathematics, and most calculations depend on them. In what category does a circle fall, and what defines a function? Let us break it down;

Is A Circle A Function?

No, any mathematical expression of a circle will be an equation, not a function. A function needs to have only one output for a given set of inputs, but a circle does not obey this rule since it has more than one output for one value on a Cartesian plane. You, therefore, can’t describe a circle as a function.

What Is A Function?

Functions are one of the most important pillars of calculus, and you use them every day. Functions map a series of numbers to a different set of numbers, but what does this mean? 

If you have a function and put in a number like 5, you get, say, 8; if you put in a number 6, you get a number 20. 

For each number you put in, say X, you will get another number, say, Y. Sometimes, you can put in two numbers and get the same number out.

When dealing with a function, there is no point at which you will put one number and get two different numbers as outputs. 

You use functions when going to the gas station; the amount you pay relies on the amount of gas you pump.

The function maps the number of gallons you pump to the number of dollars you should pay.  You know the X variable, the independent variable, the number of gallons you intend to buy.

You want to know the dollars you will pay for it since it is a dependent variable Y; it depends on the gallons you need. Mathematically speaking, the dollars you pay are the function of the gallons of fuel you buy.

In this case, you take two inputs, the price of fuel per gallon and the number of gallons you intend to purchase, and you take them through a function to get one output. The fuel price per gallon is a constant, which doesn’t change in the function but affects the output.

If you buy more gallons of fuel, you will pay more money since the variable will increase, but the constant will remain. This ensures that a series of numbers are subject to the same conditions and give one output.


A circle is not a function, and you can’t express it as such mathematically; it is an equation. Functions are a crucial part of life, and we use them in figuring out how much to pay for goods, fuel, and so much more. It is an integral part of life that we use without noticing.


Please enter your comment!
Please enter your name here