## Surjective function

### Set

context | $X,Y$ |

definiendum | $f\in$ it |

inclusion | $f:X\to Y $ |

postulate | $\text{im}(f)=Y $ |

### Discussion

A function can only be or not be surjective w.r.t. to a stated codomain. A function is always surjective w.r.t. it's own image. See Function for further discussion.