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.

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.
gas

Sentence1: an earthquake causes the ground to shake. 
Sentence2: A number of buildings in Istanbul also were damaged in the earthquake.
earthquake

Sentence1: a meter stick is used to measure distance. 
Sentence2: 100 cm is a meter.

meter