Cardinality Comparison
QUESTION
Cardinality Comparison
Click to reveal answer ANSWER
$\text{card } X \le \text{card } Y$ if there exists an injection from $X$ to $Y$ (or if $X \neq \emptyset$, a surjection from $Y$ to $X$).
- Strict inequality $\text{card } X < \text{card } Y$ holds if there is no injection from $Y$ to $X$.
Click to see question - ソースノート: chapter1.md
- カードID: cardinality-comparison
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