5.10.6 ‘@9’: Make index entry (user-defined format)

The construction ‘@9Text@>’ is used to create an index entry in a format defined by the user. It is associated with the macro \9, which will be called during TeX’s processing of the Index as \9{Text}. The user must define \9 according to the format

\def\9#1{...}

where argument ‘#1’ is the text between ‘@9’ and ‘@>’. For example, to print that text in a sans serif font, say

\def\9#1{{\sf #1}}

(Note the extra level of braces to prevent the font command from propagating.)