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: Rainy clouds cause rain, and excess water vapor from clouds is the basis of rainbows. 
Sentence2: Condensation can lead to rain.

Ex Output:
rain


Ex Input:
Sentence1: Unequal heating by the sun s rays causes differences in temperature. 
Sentence2: Differences in temperature causes global wind patterns.

Ex Output:

differences