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: friction causes the temperature of an object to increase. 
Sentence2: internal combustion engines get hot.
Example Output: temperature

Example Input: Sentence1: Sand and mud are examples of sediments. 
Sentence2: layers of sand over the remains of organisms over time can create fossils.
Example Output: Sand

Example Input: Sentence1: friction causes the speed of an object to decrease. 
Sentence2: friction causes pressure increases.
Example Output:
causes