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.

[Q]: Sentence1: Many birds perform elaborate courtship dances. 
Sentence2: Many birds perform dances before they mate.
[A]: Many


[Q]: Sentence1: if an organism becomes too hot then that organism may die. 
Sentence2: a plant can collapse if it gets too hot.
[A]: hot


[Q]: Sentence1: Copper is a great thermal conductor. 
Sentence2: if copper is exposed to a source of heat then it may become hot.
[A]:
Copper