What is the meaning of logos?

Logos is a Greek word generally used, in the context of rhetoric, to describe an appeal to logic. When somebody is trying to argue a point, for example, he or she might rely on logic, or logos, to convince the other person of the point. Logos is also used as a persuasive tool in advertising, and it is often characterized by the use of facts, figures, and statistics. An advertisement selling mouthwash, for example, might claim that the mouthwash will kill 99.9% of the germs that cause bad breath.
Logos is also often characterized by the delineation of a cause and effect process. For example, a teacher might tell a student that his or her grades will suffer if they do not complete their homework on time, or a coach might tell a basketball team that their chances of winning the next game will increase if they spend more time training. In both cases, logic is being used as a persuasive tool.