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: Visible and invisible light is energy in the form of electromagnetic waves. 
Sentence2: Eyes are used for seeing animals by sensing electromagnetic waves.

Answer: electromagnetic


Question: Sentence1: friction causes the temperature of an object to increase. 
Sentence2: internal combustion engines get hot.

Answer: temperature


Question: Sentence1: threatening behavior by predators causes a porcupine to extend its quills. 
Sentence2: threatening behavior by predators causes a rodent to extend its quills.

Answer:
behavior