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: keeping food cold is used for keeping food fresh. 
Sentence2: Keeping food at 40 degrees F or lower is used for keeping food fresh.

SOLUTION: food

PROBLEM: Sentence1: if an object in a fluid is more dense than that fluid then that object will sink in that fluid because of gravity. 
Sentence2: Most seeds are more dense than water.

SOLUTION: dense

PROBLEM: Sentence1: water vapor condensing in clouds causes rain. 
Sentence2: water vapor condensing in clouds causes liquid precipitation?.

SOLUTION:
clouds