This question came up as an objection to the way I suggested to build an index. It would consist of entries like: <a href="dictionary.html#d_somenumberX">dictionary</a>, with a corresponding anchor in the text. There was concern that the index might end up larger than the dictionary.
I looked at the WordNet dictionary, and the entries seemed to average at least twice as long as that link.
Anyway, that's just one possible way an index might be built. I don't know that we'll use it.