instruction:
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.
question:
Sentence1: Many birds perform elaborate courtship dances. 
Sentence2: Many birds perform dances before they mate.
answer:
Many


question:
Sentence1: dew is formed when water vapor condenses over night. 
Sentence2: When water vapor condenses overnight, the temperature has reached the dew point.
answer:
condenses


question:
Sentence1: Heat is caused by molecules moving. 
Sentence2: molecules moving causes thermal expansion.
answer:

molecules