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: Mutations are essential for evolution to occur. 
Sentence2: Genes are altered for evolution to occur.

Answer: evolution


Question: Sentence1: All monkeys are mammals. 
Sentence2: monkeys conserve body heat with their hair or fur.

Answer: monkeys


Question: Sentence1: natural magnetism is used for pointing north by a compass. 
Sentence2: fields make compasses point north.

Answer:
compass