\DeclareMathSymbol {<symbol>} {<type>} {<sym-font-name>}
{<slot>}
The <symbol> can be either a single character such as `>>', or a
macro name, such as \sum.
Defines the <symbol> to be a math symbol of type <type> in slot <slot> of symbol font <sym-font-name>. The <type> can be given as a number or as a command:
Only symbols of type \mathalpha will be affected by math alphabet
commands: within the argument of a math alphabet command they will
produce the character in slot <slot> of that math alphabet's font.
Symbols of other types will always produce the same symbol
(within one math version).
\DeclareMathSymbol allows a macro <symbol> to be redefined only if
it was previously defined to be a math symbol. It also checks that
the <sym-font-name> is a declared symbol font.
Example:
\DeclareMathSymbol{\alpha}{0}{letters}{"0B}
\DeclareMathSymbol{\lessdot}{\mathbin}{AMSb}{"0C}
\DeclareMathSymbol{\alphld}{\mathalpha}{AMSb}{"0C}
\DeclareMathDelimiter {<cmd>} {<type>}
{<sym-font-name-1>} {<slot-1>}
{<sym-font-name-2>} {<slot-2>}
Defines <cmd> to be a math delimiter where the small variant is in slot <slot-1> of symbol font <sym-font-name-1> and the large variant is in slot <slot-2> of symbol font <sym-font-name-2>. Both symbol fonts must have been declared previously.
Checks that <sym-font-name-i> are both declared symbol fonts.
If TeX is not looking for a delimiter, <cmd> is treated just as
if it had been defined with \DeclareMathSymbol using
<type>,<sym-font-name-1> and <slot-1>. In other words, if a
command is defined as a delimiter then this automatically defines it
as a math symbol.
Example:
\DeclareMathDelimiter{\langle}{\mathopen}{symbols}{"68}
{largesymbols}{"0A}
\DeclareMathAccent {<cmd>} {<type>} {<sym-font-name>} {<slot>}
Defines <cmd> to act as a math accent.
The accent character comes from slot <slot> in
<sym-font-name>. The <type> can be either
\mathord or \mathalpha; in the latter case the accent character
changes font when used in a math alphabet.
Example:
\DeclareMathAccent{\acute}{\mathalpha}{operators}{"13}
\DeclareMathAccent{\vec}{\mathord}{letters}{"7E}
\DeclareMathRadical {<cmd>}
{<sym-font-name-1>} {<slot-1>}
{<sym-font-name-2>} {<slot-2>}
Defines <cmd> to be a radical where the small variant is in slot <slot-1> of symbol font <sym-font-name-1> and the large variant is in slot <slot-2> of symbol font <sym-font-name-2>. Both symbol fonts must have been declared previously.
Example (probably the only use for it!):
\DeclareMathRadical{\sqrt}{symbols}{"70}{largesymbols}{"70}