Difference between Relation and Functions with Examples

Functions are a particular kind of relationship. So, to grasp what a function is, it is essential to know what relationships are.

So, we’re here to distinguish between Relation and Functions in a straightforward way.

Understanding relations

An equation, a relation or a graph, diagram of a list, equation, or diagram specifies a particular connection between two elements. It is a fairly formal definition of a fundamental idea. Take the relationship r as to mean:

Formula example:

r.{(-1,3), (0.9), (1,5), (2,7), (3,2)}

The word r is used to express the relationship between five pairs of numbers. An individual set of parentheses identifies each pair. Consider each parenthesis set in terms of an (input-output) pairing. In this way, the first number in each pair is the input, and the second number represents the output that r provides for the input. 

For example, if we input the number 1 into r, the equation gives you the output number of 3 because the pair (-1,3) is included in the definition of r.

The relation r isn’t intended to take all real numbers as inputs. It will only accept inputs from the set of -1, 0, 1, 2, and 3. These numbers constitute the primary piece of every pair of numbers in the definition of r. This set of possible inputs is referred to as the domain of r. 

This is the possible set of results (the second number in each pairing) such as (2, 3, 5, 7, 9). It is common to arrange the sets in order from lowest to most.

Defining functions

The term “function” refers to a relationship that has each input being one output. It is easiest to explain this visually. In Figure, you will see two related relations expressed in diagrams referred to as maps of relations. Both share identical domains, A, B, and C, and the range 1, 2. However, relation to g is a function, and h isn’t.

Formula example:

Figure 1 – Two relationships that are g and h appear very similar. However, g is a function, while the h isn’t. To find out why to take a look at the mapping paths leading to B in the relation.

In h, you can see that it is the input that B linked with two outputs that are both 1, 2. This is not permitted in the case of h being an operation. If a function is a function, each input can be connected to only the output of one element. Visually, there is only one pathway from every part of the domain and to an element in the range. 

The two relationships shown in the above Figure, the inputs C and D, yield the same output of 3. This is a common practice for functions. Two roads can lead to one output. However, two roads are not able to lead to an input.

A particular term is reserved for a particular function where every output results from a unique input. This means that you have only one route from every input and only one route going into every output. The functions are described as one-to-one.

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Writing functions

If all relationships were written in ordered pair formats or as visual maps, it would be easy to determine which functions are. But, it could be a hassle and uninspiring to write functions that contained more than a few components of range or domain. So, the majority of functions are written in the notation of functions. 

Consider, for instance, the function y = 2. You know that y is an x-dependent function because there is only one output for each number x you plug into x. In function notation, the function appears as the following: f( x) = x 2.

Function notation can be useful due to two reasons:

  • It includes the name of the purpose.
  • It’s easy to determine the value you’re adding to the function.

Example 1: Examine the formula that f( x) = 2 x 2 + + 3 for the case that x = -1.

Evaluation of the function for x = -1 is equivalent to discovering the function f(-1). Input -1 wherever you can see an x

There are times when you’ll see piecewise-defined functions. These are functions whose definition rules alter depending on the input value. They are typically written in this manner:

For the case of f( x), all inputs that are lower than (a) have to be connected to the variable (g). In other words, If c is greater than and it is f( C) equals the value g( C). However, if your input is more than or equivalent to a number, the formula h( x) provides the right output for the function f.

Remember that the inequality limitations depend on the value you input and not how the functions function.

Example 2: Identify the following values for


  • g(−2)

The fundamental rule for g is to change from 6xx to xx 3. Once your input is greater, 1. Since your input has a value of -2, it is recommended to stick with the first rule: x + 6.


  • g(1)

It is important to note that g derives its value by using the formula x+6 when the input is less than one or greater than 1


  • g(5)

If the input is greater than 1, then you apply x + 3 to find the value for g.

Now you know enough to identify if the relations have the right characteristics to count as functional.

Example 3: Discuss why in each of the following relationships that y is not the function of the x.


x 2 + y 2 = 9

Start by solving for y:

Note that any input valid that is x (except for the case of x = -3 or 0 or 3) will produce two outputs. If, for example, the x value is 2 and 2, then.

Remember, functions can provide only a single output per input.


If x equals 0., the function produces two outputs. Note that both conditions in the piecewise definition are 0, which means that y is 3 and -1 if x is zero. Since one input is not able to have two corresponding outputs and this isn’t an operation.

The Conclusion

So, we covered all vital points that come under the differences between relations and functions, and now, understanding and preparation are all up to you. The examples that we provided you will help you out!

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