Complex sentence: Any injective function between two finite sets of the same cardinality is also a surjection, and similarly any surjection between two finite sets of the same cardinality is also an injection.
Split into simpler sentences: Any injective function between two finite sets of the same cardinality is also a surjective function (a surjection). Similarly, any surjection between two finite sets of the same cardinality is also an injection.