Hot answers tagged indexing
I would say it depends on how the item is discussed in the body of the book. If a Markov chain is something referred to as a single entity, then index it as a single item. If you discuss several of them at once, or generalize (like saying "black holes have thus-and-such properties"), I'd use the plural.
Keep in mind that you are talking about creating concordances, not subject indexes. Subject indexes cannot be done automatically but require human analysis for substance and quality. For quality results, a good search will search both the text and the human-created index, thereby giving you both concordance findings as well as analysis for relations, ...
It might be worth employing the services of a professional indexer to create the index as a separate document, rather than generate the index from embedded codes. The types of difficulties that you have noted are familiar to indexers. An index written by an indexer is probably only applicable to a PDF though.
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