Logic (from the Ancient Greek: λογική, romanized: logikḗ) is the systematic study of the forms of inference, the relations that lead to the acceptance of one proposition, the conclusion, on the basis of a set of other propositions, the premises. More broadly, logic is the analysis and appraisal of arguments. The premises may or may not support the conclusion; when they do not, the relation is characterized as a fallacy.
In ordinary discourse, inferences may be signified by words such as therefore, thus, hence, ergo, and so on.
There is no universal agreement as to the exact definition and boundaries of logic, and this is why the issue still remains one of the main subjects of research and debates in the field of philosophy of logic (see § Rival conceptions, below). However, it has traditionally included the classification of arguments, the systematic exposition of the logical forms, the validity and soundness of deductive reasoning, the strength of inductive reasoning, the study of proof and inference (including paradoxes and fallacies), and the study of syntax and semantics.
Historically, logic has been studied in philosophy (since ancient times) and mathematics (since the mid-19th century). More recently, logic has been studied in cognitive science, which draws on computer science, linguistics, philosophy and psychology, among other disciplines.