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.

Ex Input:
Sentence1: Marine dolphins are endangered by fishing nets, speedboats, and pollution. 
Sentence2: dolphins live mainly in shallow coastal waters.

Ex Output:
dolphins


Ex Input:
Sentence1: Plants exhibit phototropism, or growing toward a light source. 
Sentence2: Phototropism means growing toward the energy of light.

Ex Output:
phototropism


Ex Input:
Sentence1: Arthropods are the largest phylum of invertebrates. 
Sentence2: Insects are in the phylum Arthropoda.

Ex Output:

phylum