The word Stemming refers to the process of stripping off endings of words at query/index time so that different search terms will match and retrieve documents containing related words in the index. A hypothetical example of this would be the reduction of the related words “diet”, “diets”, “dieting”, “dieted”, “dietary”, “dietician”, “dieticians”, etc to a single stem “diet” which would allow a query for any one of these words to be matched against documents containing any of the other words. Computational implementations of stemming are typically not based on linguistic notions of stem and affix, but rather just frequently occurring character sequences.
Truncation or Stemming
Truncation or stemming is used to expand research by retrieving the potential variations of a keyword that use the same root or stem. Use to find different forms of words in a Boolean or keyword search. Some databases use the asterisk, some use a dollar sign, and others use the question mark. The symbol may represent one character or they could represent multiple characters. They usually apply to word endings. They may or may not apply at the beginning or middle of a word. Check the help function of the database you are using to learn the truncation symbol and rules.
Terror* will retrieve - terror, terrorist, terrorism, terrorizing, etc.
The most common truncation symbols are * and ?
Be sure to think through the logic results before doing this as you may get unwanted words - for example:
You might want navy, navies or naval so you decide to try NAV* as the root but you will also get navigating, navigation, etc.
You are looking for police or policing so you decide to try POLIC* as the root/stem but you will also get policy or policies, etc.