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: a flashlight converts chemical energy into light energy. 
Sentence2: Chemical energy converted to light energy requires batteries.
chemical

Sentence1: gills are used for breathing water by aquatic animals. 
Sentence2: gills are used for breathing water by sharks.
are

Sentence1: rocks interacting with wind over long periods of time causes weathering. 
Sentence2: On Earth, rocks are weathered by wind and water, creating soil and sand.

weathering