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: Combustion generates toxic fumes. 
Sentence2: High temperatures can cause toxic fumes.
Example Output: fumes

Example Input: Sentence1: plant requires seed dispersal for reproduction. 
Sentence2: plants are pollinated by birds.
Example Output: plant

Example Input: Sentence1: Bamboos are vigorous, rugged plants. 
Sentence2: bamboo have specialized reproductive organs.
Example Output:
Bamboos