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$\mathrm c$

The Système Internationale d'Unités symbol for the metric scaling prefix centi, denoting $10^{\, -2 }$, is $\mathrm { c }$.

Its $\LaTeX$ code is \mathrm {c} .

Speed of Light


The speed of light (in a vacuum) is a physical constant.

Information cannot travel faster.

It is usually denoted $c$, and its value is given as:

$c = 299 \, 792 \, 458 \text { m s}^{-1}$


The metre is in fact defined in terms of the speed of light and the definition of the second.

Its $\LaTeX$ code is c .


$\mathrm C$ or $\mathrm c$

The hexadecimal digit $12$.

Its $\LaTeX$ code is \mathrm C  or \mathrm c.

Roman Numeral

$\mathrm C$ or $\mathrm c$

The Roman numeral for $100$.

Its $\LaTeX$ code is \mathrm C  or \mathrm c.


$\mathrm C$

The symbol for the coulomb is $\mathrm C$.

Its $\LaTeX$ code is \mathrm C .

Set of Complex Numbers


The set of complex numbers.

The $\LaTeX$ code for \(\C\) is \C  or \mathbb C or \Bbb C.

Set of Non-Zero Complex Numbers

$\C_{\ne 0}$

The set of non-zero complex numbers:

$\C_{\ne 0} = \C \setminus \set 0$

The $\LaTeX$ code for \(\C_{\ne 0}\) is \C_{\ne 0}  or \mathbb C_{\ne 0} or \Bbb C_{\ne 0}.

Extended Complex Plane

$\overline \C$

The extended complex plane $\overline \C$ is defined as:

$\overline \C := \C \cup \set \infty$

that is, the set of complex numbers together with the point at infinity.

The $\LaTeX$ code for \(\overline \C\) is \overline \C  or \overline {\mathbb C} or \overline {\Bbb C}.

Relative Complement

$\relcomp S T$ or $\map {\mathcal C_S} T$

Let $S$ be a set, and let $T \subseteq S$, that is: let $T$ be a subset of $S$.

Then the set difference $S \setminus T$ can be written $\relcomp S T$, and is called the relative complement of $T$ in $S$, or the complement of $T$ relative to $S$.


$\relcomp S T = \set {x \in S : x \notin T}$

The $\LaTeX$ code for \(\relcomp S T\) is \relcomp S T .

The $\LaTeX$ code for \(\map {\mathcal C_S} T\) is \map {\mathcal C_S} T .

Set Complement

$\map \complement S$ or $\map {\mathcal C} S$

The set complement (or, when the context is established, just complement) of a set $S$ in a universe $\mathbb U$ is defined as:

$\map \complement S = \relcomp {\mathbb U} S = \mathbb U \setminus S$

See the definition of Relative Complement for the definition of $\relcomp {\mathbb U} S$.

The $\LaTeX$ code for \(\map \complement S\) is \map \complement S .

The $\LaTeX$ code for \(\map {\mathcal C} S\) is \map {\mathcal C} S .

Hyperbolic Cosine


$\operatorname {ch}$

Hyperbolic cosine.

A variant of $\cosh$.

Its $\LaTeX$ code is \operatorname {ch} .

Inverse Hyperbolic Cosine


$\operatorname {ch}^{-1}$

Inverse hyperbolic cosine.

A variant of $\cosh^{-1}$.

Its $\LaTeX$ code is \operatorname {ch}^{-1} .


$\mathrm {cm}$

The symbol for the centimetre is $\mathrm {cm}$:

$\mathrm c$ for centi
$\mathrm m$ for metre.

Its $\LaTeX$ code is \mathrm {cm} .