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: a greenhouse is used to protect plants by keeping them warm. 
Sentence2: Flower size varies by plant.
[EX A]: plants

[EX Q]: Sentence1: Autumn brings the changing of the seasons. 
Sentence2: Earth 's tilt on its rotating axis causes autumn.
[EX A]: Autumn

[EX Q]: Sentence1: smoking tobacco decreases stamina. 
Sentence2: smoking cigars decreases stamina.
[EX A]:
decreases