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.

Ex Input:
Sentence1: Metabolic rate is the rate at which food is burned for energy. 
Sentence2: thyroid hormones increase the rate of energy consumption.

Ex Output:
energy


Ex Input:
Sentence1: a pulley is used for lifting objects. 
Sentence2: Resistance exercises are weight-lifting exercises.

Ex Output:
lifting


Ex Input:
Sentence1: Competition may lead to aggressive behaviors or displays of aggression. 
Sentence2: Frequently their behavior is aggressively hostile.

Ex Output:

aggressive