\DeclareMathAlphabet {<math-alph>} {<encoding>} {<family>}
{<series>} {<shape>}
If this is the first declaration for <math-alph> then a new math
alphabet with this as its command name is created.
The arguments <encoding> <family> <series> <shape> are used to
set, or reset, the default values for this math alphabet in all math
versions; if required, these must be further reset later for a
particular math version by a \SetMathAlphabet command.
If <shape> is empty then this <math-alph> is declared to be invalid
in all versions, unless it is set by a later \SetMathAlphabet
command for a particular math version.
Checks that the command <math-alph> is either already a math alphabet
command or is undefined; and that <sym-font> is a symbol font.
In these examples, \foo is defined for all math versions but \baz,
by default, is defined nowhere.
\DeclareMathAlphabet{\foo}{OT1}{cmtt}{m}{n}
\DeclareMathAlphabet{\baz}{OT1}{}{}{}
\SetMathAlphabet {<math-alph>} {<version>}
{<encoding>} {<family>} {<series>} {<shape>}
Changes, or sets, the font for the math alphabet <math-alph> in math version <version> to <encoding><family><series><shape>. Checks that <math-alph> has been declared as a math alphabet, <version> is a known math version and <encoding> is a known encoding scheme.
This example defines \baz for the `normal' math version only:
\SetMathAlphabet{\baz}{normal}{OT1}{cmss}{m}{n}
Note that this declaration is not used for all math alphabets:
Section 3.5 describes \DeclareSymbolFontAlphabet,
which is used to set up math alphabets contained in fonts which have
been declared as symbol fonts.