\begin{align} &\mathbb{N} = \{0, 1, 2, 3, \ldots\} \\ &\mathbb{Z} = \{0, \pm 1, \pm 2, \pm 3, \ldots \} \\ &\mathbb{Q} = \rm Rational \; Numbers \it \\ &\mathbb{R} = \rm Real \; Numbers \it \\ &\mathbb{C} = \rm Complex \; Numbers \it \\ &\mathbb{Z}_n = \mathbb{Z} \; \mod \; n \\ &\Rightarrow \rm \; is \; read \; ``implies"\\ &\rm iff \; is \; read \; ``if\; and \; only \; if" \\ &\forall \rm \; is \; read \; ``for \; every" \\ &\exists \rm \; is \; read \; ``there \; exists" \\ &\in \; \rm is \; read \; ``in" \\ &\ni \; \rm is \; read \; ``such \; that" \\ &\dot{=} \; \rm is \; ``represented \; by" \\ &\subset \; \rm is \; ``subset\; of" \\ &\equiv \; \rm is\;``defined\; as" \\ &= \quad \text{exactly equal} \notag \\ &\propto \quad \text{equality except perhaps for a factor with dimension} \notag\\ &\sim \quad \text{equality except perhaps for a factor without dimensions} \notag \\ &\approx \quad \text{equality except perhaps for a factor close to 1} \end{align}