Simple formulas

Normal letters and standard symbols are typeset simply by using the letters directly or using a command that denotes the wanted symbol. So $\sum A_{i}$ will produce A_i. The typeface chosen will depend on the current 〈math version〉. You can switch between 〈math versions〉 outside of math mode,⁷ thereby changing the overall layout of the following formulas.

L^ATEX knows about two math versions called `normal' and `bold'. As the name indicates, \mathversion{normal} is the default. In contrast, the bold version will produce bolder letters and symbols. This might be suitable in certain situations like headings, but recall that changing the version means changing the appearance (and perhaps the meaning) of the whole formula. If you want to bolden only some symbols or characters within one formula you should not change the \mathversion. Instead you should define a special math alphabet for characters (see below) and/or use the command \boldsymbol which is provided by the document style option amsbsy. For historical reasons L^ATEX maintains two abbreviations to switch to its math versions: \boldmath and \unboldmath.

Other versions could be provided in special style options. For example the `concrete' option mentioned before sets up a version called `euler' to typeset formulas in the same way as it was done in [4].