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.

Q: Sentence1: Precipitation falls on the windward side of the mountain range. 
Sentence2: Mountains have higher precipitation than adjacent lowlands.

A: Precipitation
****
Q: Sentence1: measuring the hardness of minerals requires scratching those materials. 
Sentence2: To figure out the hardness of a mineral, the Moh's scale of hardness is used.

A: minerals
****
Q: Sentence1: On the outside is a protective skin of bark made mainly of cork. 
Sentence2: Trees have woody stems covered with protective skin.

A:
protective
****