Metamorph's whole search process is built around its ability to deal with root morphemes in words, and in fact the program was originally christened "Metamorph" based on that ability. An inherent part of the search process is to take search words, strip them of suffixes and prefixes down to a recognizable morpheme, search for the morpheme, find a possible match, then go through the process again with the possible match to see if it is indeed what you were looking for.
The elements which affect morpheme processing are very subtle as they affect all language and therefore all of any text you are searching. Therefore, any changes entered into the defaults which dictate how or whether morpheme processing is done, will affect broadly the nature of your search results.
The options which affect morpheme processing are the following:
The content of the Equiv-Suffix
List determines which suffixes
will be stripped before doing lookup for a matching entry in the
Equivalence File.
The content of the Prefix
and Suffix
Lists determines
precisely what will be stripped from a search word to obtain the
morpheme which is passed to the Search Engine. Specifically this
relates to all words in all equivalence sets.
To understand why the program is doing what it is doing you need to know more than just what is contained in the lists; you must also understand the sequence of the Morpheme Stripping process. If you understand these rules, you will have better judgment on how to edit the prefix and suffix lists, what happens when you turn off prefix and/or suffix processing altogether, what happens if you turn off the morpheme rebuild step, and where the minimum word length setting comes in.