11.6 Words in mathematics

Most of the time formulas consist only of symbols and individual letters denoting variables. However, sometimes ordinary text is made part of a formula, either to annotate some part of it or to continue the outer text with words like “and”, etc. In addition, a number of common operators are typeset using words rather than symbols.

11.6.1 The - text command

Math font-changing commands such as are not intended for putting normal text inside mathematics as the fonts used are fixed and may not bear any relation to the font used in the text surrounding the formula. To produce “text” fonts inside a formula in standard LaTEX you can use etc., or you can simply use if you want to typeset in the font used outside the current mathematical material. However, one problem with all these commands in standard LaTEX is that they always typeset their text in a fixed font size, regardless of the position in the formula.

The amsmath package improves1 on this by additionally providing the command , which is similar to but is much better, ensuring that the text is set using the correct font size. It also modifies nd friends to change the font size as necessary, as can be observed in the next example:

11.6.2 Operator and function names

The names of many well-known mathematical functions (such as log and sin) and operators (such as max and lim) are traditionally typeset as words (or abbreviations) in roman type so as to visually distinguish them from shorter variable names that are set in “math italic”. The most common function names have predefined commands to produce the correct typographical treatment; see Table 11.6 on the next page. Most functions are available in standard LaTEX; those listed in blue in the table require loading amsmath. The functions marked with (ℓ) may “take limits” in display formulas (see Section 11.4.4).