The difference between negligence and gross negligence is that gross negligence is a conscious and voluntary action, while simple negligence is the failure to exercise reasonable care. The two differ in the degree of inattention exhibited by the perpetrator.
Negligence and gross negligence both refer to the same action and are defined as the disregard for the safety or lives of others. The major differentiation is the degree to which the disregard occurred. That degree is not quantifiable, but it is instead decided based on precedent that has been set in previous course cases. Precedent is a common means for differentiating parts of the law.