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: Warm temperatures have helped plant growth and sizing. 
Sentence2: a greenhouse helps  plant growth.

Answer: growth


Question: Sentence1: Coral reefs are made up of the accumulated exoskeletons of the coral polyp. 
Sentence2: coral polyps form reefs.

Answer: polyp


Question: Sentence1: knowledge of the stars can be used to navigate. 
Sentence2: And every star there ever was is in a constellation.

Answer:
stars