Task: Paraphrasing
Input (English): Question: Newton’s second law of what is more than a definition; it is a relationship among acceleration, force, and mass? 
Answer: motion. 
Sentence: Newton’s second law of motion is more than a definition; it is a relationship among acceleration, force, and mass.
Output (English): The relationship of acceleration, force, and mass is what's known as Newton's second law of motion.