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.

Input: Consider Input: Sentence1: friction causes an object to lose energy. 
Sentence2: Friction occurs when surfaces rub together.

Output: friction


Input: Consider Input: Sentence1: Streams may start with runoff or water seeping out of a spring. 
Sentence2: Most water comes from precipitation.

Output: water


Input: Consider Input: Sentence1: When it rains, the roots absorb water quickly and the plants store the water in the stems. 
Sentence2: Some plants store water after absorbing it with the roots.


Output: absorb