Keyword Stemming and Tools
Keyword Stemming in regards to PPC, is taking the stem of a word, and building additional words by adding a prefix or suffix and using pluralization.
Sometimes the words from the output of these keyword stemming tools don’t have any meaning. That’s because the keyword stemming tools are meant to strip a word down to the root and show different variations of the word form.
So, the solution is for the keyword stemming tools to cross-reference the output against a huge dictionary of words (like Merriam Webster Dictionary) to insure that the output is linguistically correct words.
An example of Keyword stemming for the word “search†is:
search
searcher
searches
searched
searching
searchable
Keyword Stemming tools are very useful for expanding keyword lists. Some of these keyword stemming tools will give you the equivalent of long tail keywords. My suggestion is to use keyword matching options to increase your conversion rates. Bear in mind, that most 2nd tier search engines won’t have the keyword inventory. So, keyword stemming is a better strategy on the large engines like Google & Yahoo rather than smaller engines like Ask.
http://www.related-pages.com/adWordsKeywords.aspx  Keyword Stemming tool