# SP20:Lecture 8 prep

This lecture we will discuss cardinality.

Please come to lecture with the following definitions (it helps to draw yourself a picture of a surjection or an injection to see which corresponds to or ):

Definition:
If and are sets, then means that there exists an injection
Definition:
If and are sets, then means that there exists a surjection
If and are sets, then means that there exists a bijection