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: an animal usually requires a warm body temperature for survival. 
Sentence2: Warm blooded animals have a constant body temperature.
[EX A]: animal

[EX Q]: Sentence1: powering an electrical device with a battery requires a path for electricity to flow through a closed circuit. 
Sentence2: An electrical current is a flow of electrons.
[EX A]:
electrical