Keyword stemming is the process of finding keyword variations (plurals, synonyms, related concepts, etc.). We know that Google scans HTML body content to find which ad to display.In the process of extracting keywords to match corresponding ads, does Google perform stemming of these keywords to select ads for display?
Does Google use keyword stemming for ad selection?
google;keywords;advertising
When advertisers choose broad match on the keywords they bid on, Google does much more than stemming.  In that case it also shows the ad on synonyms and related concepts.