A fallacy is generally considered to be an error in reasoning. It refers both to the failure to apply logic to a line of thought, and to the use of problematic arguments. The term can be applied when dealing both with informal and formal logic, although it usual refers to the former.
An informal fallacy refers to a flawed argument, where the premises do not support the conclusion. It can, however, have a valid logical format. This type of fallacy is commonly divided in two main groups: material fallacies and verbal fallacies.
Material fallacies, concerned with the content of the argument, can be divivided following Aristotle's taxonomy from his work Organon. One such example is the famous Straw Man fallacy:...