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.

[EX Q]: Sentence1: Mating is generally preceded by courtship. 
Sentence2: Mating is generally similar across species.
[EX A]: Mating

[EX Q]: Sentence1: if a habitat can no longer support animals then those animals will move to another area. 
Sentence2: Each species of animal is unique.
[EX A]: animals

[EX Q]: Sentence1: Friction occurs when two substances rub together. 
Sentence2: two substances rubbing together causes an object to lose energy.
[EX A]:
rub