>>39
Although,
>>37 did say measure, instead of cardinality. But being able to or not being able to map one set into another injectively is related to cardinality, rather than measure.
>>40
There are other constructions too. The construction itself isn't that important, but the high level properties that are true about them. It's good to know that there is at least one low level construction so that logical paradoxes can be avoided when assuming their existence.