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: friction causes the temperature of an object to increase. 
Sentence2: When we increase the temperature of objects, they always expand.

Answer: increase


Question: Sentence1: friction causes the temperature of an object to increase. 
Sentence2: Friction causes the temperature of a toy to increase.

Answer: causes


Question: Sentence1: An insect is a small animal with six legs. 
Sentence2: Most arthropods are small animals with six legs.

Answer:
animal