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: healing requires rest. 
Sentence2: healing requires time.
Example Output: healing

Example Input: Sentence1: Plants use unsaturated fatty acids to store energy. 
Sentence2: Plants and fish contain fatty acids.
Example Output: Plants

Example Input: Sentence1: braking can cause skidding. 
Sentence2: braking on bald tires can cause wet weather accidents.
Example Output:
braking