# Math Help - Injective Function

1. ## Injective Function

Hi. Is a function injective iff EVERY element in the domain is mapped to a distinct element in the codomain:

For example:

A={1,2,4} B={Q, W, S, T}

1 is mapped to Q
2 is mapped to W
4 is not mapped.

Is this considered an injective function from A to B?

2. Originally Posted by jayshizwiz
Hi. Is a function injective iff EVERY element in the domain is mapped to a distinct element in the codomain:

For example:

A={1,2,4} B={Q, W, S, T}

1 is mapped to Q
2 is mapped to W
4 is not mapped.

Is this considered an injective function from A to B?
The given function is not a function from A to B, but rather a function from {1,2} to B. So, no.

3. The given function is not a function from A to B, but rather a function from {1,2} to B. So, no.
Thanks.

4. Notice that the difficulty is not with "injective" but calling it a function from A to B at all.