Sentence:  There are actually "three" <WSD>sweet spots</WSD> on a racquet's face. Each <WSD>sweet spot</WSD> measures a different physical characteristic of your racquet. The <WSD>sweet spot</WSD> that most of us think of is the place on the strings where the ball rebounds with the most power, or, technically, the post on the racquet with the maximum coefficient of restitution. The second <WSD>sweet spot</WSD> is where the least amount of shock is given to your hand and arm. This is known as the center of percussion. The third <WSD>sweet spot</WSD> is the node or place where the least amount of vibration occurs after the initial ball impact. Normally all three <WSD>sweet spots</WSD> do not occur in the same location. 
Meaning of the word marked with <WSD> tags:  Any of several places on a bat, racquet, etc., with which to hit a ball, resulting in the latter rebounding with some optimal desirable effect, such as minimum vibration or maximum velocity.