Let $(X, \mathcal{F}, \mu)$ be a measure space. Then:
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1. **Monotonicity:** If $A, B \in \mathcal{F}$ with $A \subset B$, then $\mu(A) \le \mu(B)$.
2. **Excision:** If $A, B \in \mathcal{F}$ with $A \subset B$ and $\mu(A) < \infty$, then $\mu(B \setminus A) = \mu(B) - \mu(A)$.
3. **Countable subadditivity:** If $A_1, A_2, \ldots \in \mathcal{F}$ (not necessarily disjoint), then