The science of reasoning is called the logic.In mathematics.In Logic, We use symbols and notations to denote words or sentence, hence it is also called symbolic logic or mathematical logic.The statement which declares one thing at a time is called a simple statement.when two or more than two simple statements are combined to form a statement, it is called compound statement. The truthness or falsity of a statement is called its truth value. The word or phrases, ''and '', ''or'', ''if ..... they'' and ''if and only if'' are the logical connectives used to combine simple statements to form compound statements.