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: Ovulation is the release of an egg from an ovary. 
Sentence2: The release of an egg during ovulation is used in reproduction.

Answer: Ovulation


Question: Sentence1: Rivers, rainwater, well water and most lakes contain fresh water. 
Sentence2: canyons are formed by rainwater.

Answer: rainwater


Question: Sentence1: Rabbits' brown summer fur is replaced with fur that is greyer. 
Sentence2: If seeds stick to a rabbit then that seed will be transported by the animal.

Answer:
Rabbits'