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: Mollusks are invertebrates such as the common snail. 
Sentence2: Another common snail is the decollate snail.
Example Output: snail

Example Input: Sentence1: Smoking accelerates the aging process. 
Sentence2: smoking accelerates the death of cells.
Example Output: Smoking

Example Input: Sentence1: Mollusks are invertebrates such as the common snail. 
Sentence2: snails have no backbone.
Example Output:
snail