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: Many birds perform elaborate courtship dances. 
Sentence2: Many birds perform dances before they mate.

Answer: Many


Question: Sentence1: Some mollusks are nearly microscopic. 
Sentence2: Some squids are nearly microscopic.

Answer: Some


Question: Sentence1: cooking food requires adding heat energy. 
Sentence2: Metals conduct heat energy .

Answer:
energy