Fallacy

Fallacy is the use of invalid or otherwise faulty reasoning or "wrong moves" in the construction of an argument which may appear stronger than it really is if the fallacy is not spotted.

Fallacies are commonly divided into "formal" and "informal." A Formal Fallacy is a flaw in the structure of a deductive argument which renders the argument invalid, while an Informal Fallacy originates in an error in reasoning other than an improper logical form.