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.

Example Input: Sentence1: Electrical currents cause magnetic fields. 
Sentence2: Electrical currents can cause objects to repel each other.
Example Output: Electrical

Example Input: Sentence1: ultraviolet light causes sunburn. 
Sentence2: Sunburn risk is higher at elevation.
Example Output: sunburn

Example Input: Sentence1: sedimentary rocks are formed by deposition. 
Sentence2: Sandstones are another type of sedimentary rocks used in buildings.
Example Output:
rocks