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: Precipitation falls on the windward side of the mountain range. 
Sentence2: Mountains have higher precipitation than adjacent lowlands.

Ex Output:
Precipitation


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: Macroevolution is evolution over geologic time above the level of the species. 
Sentence2: Macroevolution is very, very slow evolution above the level of the species.

Ex Output:

Macroevolution