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JEE Main 2026 Preparation: Question Papers, Solutions, Mock Tests & Strategy Unacademy » JEE Study Material » Mathematics » Differences between Injective Function and Surjective Function

Differences between Injective Function and Surjective Function

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In mathematics, functions are widely used to define and describe certain relationships between sets and other mathematical objects. Furthermore, functions can be used to impose mathematical structures on sets.

If no two domain components point to the same value in the co-domain, the function is injective. A function is Surjective if each element in the co-domain points to at least one element in the domain. If a function has both injective and surjective properties.

An injection A→B maps A into B, allowing you to find a copy of A within B. A surjection  A→B maps A over B in the sense that the image spans the entire width of B. Sur” is a Latin phrase that means “above” or “above,” as in “surplus” or “survey.”

Injective and surjective functions

Injective functions

An injective function or one-to-one function is one that maps distinct elements of one domain to distinct elements of the other domain.

In summary, consider ‘f’ to be a function whose domain is set A. If for all x and y in A, the function is said to be injective.

Assume f(x) = f(y), and then demonstrate that x = y.

Assume x does not equal y and demonstrate that f(x) does not equal f. (x).

Subjective functions

A surjective function (also surjective or onto function) in mathematics is a function f that maps an element x to every element y; that is, for any y, there is an x such that f(x) = y. In other words, every element of the function’s codomain is an image of at least one element of the function’s domain.

If each element of the codomain is mapped to at least one element of the domain, the codomain is surjective or onto. In other words, each codomain element has a non-empty preimage. A function is surjective if its image is the same as its codomain.

If the range of f equals the codomain of f, the function f : A → B is surjective, or onto.R B in every function with range R and codomain B. To demonstrate that a given function is surjective, we must establish that  B R; therefore R = B will be true.

Differences of injective and surjective functions

Injective functions

Surjective functions

 

An injective function is one in which each element of Y is transferred to at most one element of X.

 

Surjective is a function that maps each element of Y to some (i.e., at least one) element of X.

 

A function is one-to-one or injective if it does not map two different elements in the domain to the same element in the range.

 

Two simple qualities that functions may possess prove to be extremely beneficial. If a function’s codomain is also its range, the function is onto or surjective.

 

function f is injective if a1a2 implies f(a1)≠f(a2)

 

If f equals its range, a function f:A→B is surjective (onto). Alternatively, for any bB, there is some  aA such that f(a)=b. This means that for any y in B, some x in A exists such that y=f (x).

Determine injectivity on a given domain.

Determine the surjectivity of a domain.

 

 

 

Example: f:N→N,f(x)=3x  is injective.

 

f:N→N,f(x)=x2 is injective.

 

Example: f:N→N,f(x)=x+2 is a surjective expression.

f:R→R,f(x)=x2 is not surjective since no real integer has a negative square.

Conclusion

In this article we conclude that Injective is also known as “One-to-One. Surjective means that for every “B” there is at least one “A” that matches it, if not more. We won’t have two or more “A” pointing to the same “B” because it’s injective. Surjective means that for every “B” there is at least one matching “A.” (maybe more than one). Informally, an injection has at most one input mapped to each output, a surjection has the complete possible range in the output, and a bijection has both criteria true.

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Get answers to the most common queries related to the IIT JEE Examination Preparation.

How do you determine whether a function is Injective or Surjective?

Answer:. To demonstrate that a function is injective, we must either: Assume f...Read full

Is it true that all injective functions are surjective?

Answer: If you have an injective function, f(a)≠f(b),...Read full

Is it possible for a function to be neither injective nor surjective?

Answer: . The constant function f : N → N ...Read full

What does the term surjective signify in mathematics?

Answer:. A surjective function (also surjective or onto function) in mathematics is a function f that maps an elemen...Read full

What exactly is injection mapping or function math?

Answer:. In mathematics, Injection is a mapping (or function) between two sets in which the domain (input) is made u...Read full

Answer:. To demonstrate that a function is injective, we must either: Assume f(x) = f(y), and then demonstrate that x = y. Assume x does not equal y and demonstrate that f(x) does not equal f. (x)

 

Answer: If you have an injective function, f(a)≠f(b), then one must be a and one must be b, indicating that the function is surjective. The same concept applies to sets of any finite size. If the size is n and it is injective, then there are n distinct elements in the range, which is all of M, indicating that it is surjective.

Answer: . The constant function f : N → N with f(x) = 1 is an example of a function that is neither injective nor surjective. The identity function  f : N → N , where f(x) = x, is an example of a function that is both injective and surjective.

 

Answer:. A surjective function (also surjective or onto function) in mathematics is a function f that maps an element x to every element y; that is, for any y, there is an x such that f(x) = y. In other words, every element of the function’s codomain is an image of at least one element of the function’s domain.

Answer:. In mathematics, Injection is a mapping (or function) between two sets in which the domain (input) is made up of all the elements of the first set, the range (output) is made up of some subset of the second set, and each element of the first set is mapped to a different element of the second set (one-to-one).

 

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