The selection of fonts within math mode is quite different to that of text fonts.

Some math fonts are selected explicitly by one-argument commands such
as `\mathsf{max}`

or `\mathbf{vec}`

; such fonts are called *math
alphabets*. These math alphabet commands affect only the font used
for letters and symbols of type `\mathalpha`

(see
Section 3.6); other symbols within the argument
will be left unchanged. The predefined math alphabets are:

Other math fonts are selected implicitly by TeX for symbols, with
commands such as `\oplus`

(producing ) or with straight
characters like `>>`

or `+`

. Fonts containing such math symbols are
called *math symbol fonts*. The predefined math symbol fonts
are:

Some math fonts are both *math alphabets* and *math symbol
fonts*, for example `\mathrm`

and `operators`

are the same font, and
`\mathnormal`

and `letters`

are the same font.

Math fonts in LaTeX have the same five attributes as text fonts:
encoding, family, series, shape and size. However, there are no
commands that allow the attributes to be individually changed.
Instead, the conversion from math fonts to these five attributes is
controlled by the *math version*. For example, the `normal`

math
version maps:

The `bold`

math version is similar except that it contains bold fonts.
The command `\boldmath`

selects the `bold`

math version.

Math versions can only be changed outside of math mode.

The two predefined math versions are:

Packages may define new math alphabets, math symbol fonts, and math versions. This section describes the commands for writing such packages.

Thu Jan 8 11:52:24 MET 1998