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: Clouds are one form of condensation. 
Sentence2: Clouds are one form of changing from a gas into a liquid by reducing heat energy.

Ex Output:
Clouds


Ex Input:
Sentence1: friction causes the temperature of an object to increase. 
Sentence2: internal combustion engines get hot.

Ex Output:
temperature


Ex Input:
Sentence1: Experiments are often done in a lab. 
Sentence2: Labs exist to make money.

Ex Output:

lab