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

Answer: phototropism


Question: Sentence1: Mollusks live in most terrestrial, freshwater, and marine habitats. 
Sentence2: Clams live in freshwater habitats.

Answer: freshwater


Question: Sentence1: Coral reefs are made up of the accumulated exoskeletons of the coral polyp. 
Sentence2: accumulated exoskeletons form in shallow tropical water.

Answer:
accumulated