what is a fallacies

You can always look up terminology at www.answers.com. Here's what you are looking for:
http://www.answers.com/fallacy

Here are some other helpful websites:
http://en.wikipedia.org/wiki/Fallacy

http://www.nizkor.org/features/fallacies/

http://www.fallacyfiles.org/

http://www.unc.edu/depts/wcweb/handouts/fallacies.html

http://www.iep.utm.edu/f/fallacy.htm

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FALLACIES is plural. You want to know what a FALLACY is. Check any of the websites given to you by Writeacher.