# Indexing some notions twice?

I'm making an Index of defined notions for my thesis (it's partly algebraic so there are dozens of notions defined through the whole text) and I think on how to index notions like trace of a Mobius transformation or side of a fundamental domain.

The nature says that the main part is the noun so it should be

``````fundamental domain
Ford
pre-Ford
Mobius transformation
rational
real
side
of fundamental domain
trace
of Mobius transformation
vertex
of fundamental domain
``````

But then it could be indexed the other way as well, because both Mobius transformation and fundamental domain are in Index anyways.

``````fundamental domain
Ford
pre-Ford
side of
vertex of
Mobius transformation
rational
real
trace of
``````

My question is whether it is confusing to merge both variants and make such terms indexed twice.

``````fundamental domain
Ford
pre-Ford
side of
vertex of
Mobius transformation
rational
real
trace of
side
of fundamental domain
trace
of Mobius transformation
vertex
of fundamental domain
``````
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I don't think this is a question about TeX or friends. There is a question about TeX in the vicinity, namely "How can I index the same thing in two different ways?" But that isn't the question you're asking… – Seamus Mar 8 '12 at 17:05

This is, also, just an opinion, but I feel like you should indeed make the index as complete as possible, since you don't know under which term the reader will be looking for a certain expression. I have no idea what your notions are about but if the reader (i.e. in the context) can be expecting them to be filed under two names, go for both.

However, you should not index the same thing twice under a different name. Decide on the one you want to use, and make another entry that just says "see [the first entry]". For instance:

Fundamental domain: ..., side of, 5,6,8,12,35, ...

Side: ..., of fundamental domain (see under Fundamental domain), ...

-

Well, this is an opinion, nothing more. I think that the main purpose of an index is to help the reader of your thesis to locate things quickly and easily. There are many ways to achieve this but I guess that certain crossrefs in the index like

```foo page 14,
`bar page 14`