Power can be defined as the ability to influence others and can come from different sources. There are five main types of power: coercive power which comes from the ability to punish others; reward power which involves the ability to give rewards; legitimate power which derives from someone's formal position or title; expert power which is based on knowledge and skills; and referent power which develops from personal characteristics that create admiration and loyalty. Each type of power has advantages and disadvantages for influencing others.