Symbols:Q

Set of Rational Numbers

 * $\Q$

The set of rational numbers.

Set of Non-Zero Rational Numbers

 * $\Q_{\ne 0}$

The set of non-zero rational numbers:
 * $\Q_{\ne 0} = \Q \setminus \left\{{0}\right\}$

Deprecated

 * $\Q^*$

The set of non-zero rational numbers:
 * $\Q^* = \Q \setminus \set 0$

Set of Non-Negative Rational Numbers

 * $\Q_{\ge 0}$

The set of non-negative rational numbers:
 * $\Q_{\ge 0} = \set {x \in \Q: x \ge 0}$

Deprecated

 * $\Q_+$

The set of non-negative rational numbers:
 * $\Q_+ = \set {x \in \Q: x \ge 0}$

Set of Strictly Positive Rational Numbers

 * $\Q_{> 0}$

The set of strictly positive rational numbers:
 * $\Q_{> 0} = \set {x \in \Q: x > 0}$

Deprecated

 * $\Q_+^*$

The set of strictly positive rational numbers:
 * $\Q_+^* = \set {x \in \Q: x > 0}$

{{LatexFor|for = \Q_+^*|code2 = \mathbb Q_+^*}|code3 = \Bbb Q_+^*}}

Probability

 * $q$

Used in conjunction with the general probability $p$:
 * $q = 1 - p$

As such, $q$ is a real number such that:


 * $0 \le q \le 1$

and
 * $p + q = 1$

Quotient Mapping

 * $q_\mathcal R$

The quotient mapping induced by $\mathcal R$:


 * $q_\mathcal R: S \to S / \mathcal R: \map {q_\mathcal R} s = \eqclass s {\mathcal R}$

where:
 * $\mathcal R \subseteq S \times S$ be an equivalence relation on a set $S$


 * $\eqclass s {\mathcal R}$ is the $\mathcal R$-equivalence class of $s$


 * $S / \mathcal R$ is the quotient set of $S$ determined by $\mathcal R$.

Also known as:
 * the canonical surjection from $S$ to $S / \mathcal R$
 * the canonical map or canonical projection from $S$ onto $S / \mathcal R$
 * the natural mapping from $S$ to $S / \mathcal R$
 * the natural surjection from $S$ to $S / \mathcal R$
 * the classifying map or classifying mapping (as it classifies the elements of $S$ into those various equivalence classes)
 * the projection from $S$ to $S / \mathcal R$