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: Plants exhibit phototropism, or growing toward a light source.
Sentence2: Phototropism means growing toward the energy of light.
Example Output: phototropism

Example Input: Sentence1: For example, in the sentence The rain destroyed the crops , The rain is the subject.
Sentence2: If weather is stormy then there is a chance of destroyed crops.
Example Output: crops

Example Input: Sentence1: Biodiversity generally increases from the poles to the equator.
Sentence2: Ecosystem complexity generally increases from the poles to the equator.
Example Output:
equator