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: Proper digestion is vital for nutrient absorption. 
Sentence2: Digestion is important for an animal's survival.

Answer: digestion


Question: Sentence1: Nonmetal elements are far fewer in number. 
Sentence2: There are 17 nonmetals on the periodic table.

Answer: Nonmetal


Question: Sentence1: Earth 's tilt on its rotating axis causes seasons to change. 
Sentence2: Earth 's tilt on its axis causes habitats to change.

Answer:
's