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 Q]: Sentence1: when a gas in an open container evaporates , that gas spreads out into the air. 
Sentence2: If you place gas in an open box it will evaporate and spread out into the air.
[EX A]: gas

[EX Q]: Sentence1: a polar bear requires a cold environment. 
Sentence2: polar bears live where there are fewer animals.
[EX A]: bear

[EX Q]: Sentence1: Aggression Aggression and violence often go together. 
Sentence2: competition may lead to violence.
[EX A]:
violence