{x}^{2} superscript {x}_{i} subscript \boldsymbol{A} bold \frac{x}{y} fraction \pm ± \times × \text{-} short minus \cdots ⋯ \begin{cases} 0 \\ 1 \end{cases} definition by Cases \; – a thick space \: – a medium space \, – a thin space \! – a negative thin space \alpha alpha \beta beta \gamma gamma \delta delta