 Fallacies can be classified strictly by either their structure or their content, such as classifying them as formal fallacies or informal fallacies, respectively.The classification of informal fallacies may be subdivided into categories such as linguistic, relevance through omission, relevance through intrusion, and relevance through presumption.On the other hand, fallacies may be classified by the process by which they occur, such as material fallacies (content), verbal fallacies (linguistic), and again formal fallacies (error in inference).