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: An accounting period is simply a period of time. 
Sentence2: seconds are used to measure a period.

Answer: period


Question: Sentence1: the emission of sulfur dioxide causes acid rain. 
Sentence2: the emission of sulfur dioxide causes soil weathering.

Answer: causes


Question: Sentence1: soil is formed by rocks eroding. 
Sentence2: Rivers aid in the formation of soil.

Answer:
formed