Indexing commands in Eplain come in pairs: one command that only writes the index entry to the `.idx' file (see above section), and one that also typesets the term being indexed. The former always starts with `s' (for "silent"). In either case, the name always includes `Idx', where I is the index letter, also described above. Eplain defines the index `i' itself, so that's what we'll use in the names below.
The silent form of the commands take a subterm as a trailing optional
argument. For example, \sidx{truth}[definition of] on page 75
makes an index entry that will eventually be typeset (by default) as
truth definition of, 75
Also, the silent commands ignore trailing spaces. The non-silent ones do not.