Often used Markdown

Space

 

latex space

$\quad$ space equal to the current font size (= 18 mu) *mu = length in latex
$\,$ 3/18 of \quad (= 3 mu)
$\:$ 4/18 of \quad (= 4 mu)
$\;$ 5/18 of \quad (= 5 mu)
$\!$ -3/18 of \quad (= -3 mu)
$\ (space after backslash!)$ equivalent of space in normal text
$\qquad$ twice of \quad (= 36 mu)

New line

inside of the expression

$a\\b$
$a\\b$

outside of the expression

a<br>b
a
b

Collective symbols

in

$\in$
$\in$

Mathmatical symbols

Sigma(sum)

$\sum_{lower}^{upper}$

$\sum_{lower}^{upper}$

$\displaystyle\sum_{lower}^{upper}$

$\displaystyle\sum_{lower}^{upper}$

Product

$\prod_{lower}^{upper}$

$\prod_{lower}^{upper}$

$\displaystyle\prod_{lower}^{upper}$

$\displaystyle\prod_{lower}^{upper}$

Formating

$\mathbb{R}$ $\mathbb{R}$