TASK DEFINITION: Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.
PROBLEM: Sentence1: the mass of an object causes the gravitational force exerted by that object. 
Sentence2: gravitational force accelerates objects.

SOLUTION: force

PROBLEM: Sentence1: Mating is generally preceded by courtship. 
Sentence2: Mating is generally similar across species.

SOLUTION: Mating

PROBLEM: Sentence1: Growth is faster during infancy than it is during puberty. 
Sentence2: puberty has slower development than infancy.

SOLUTION:
puberty