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: a switch is used to start the flow of current in an electrical circuit. 
Sentence2: The flow of electrical current powers a light bulb.
[A]: current


[Q]: Sentence1: Lymph is a fluid that leaks out of capillaries into spaces between cells. 
Sentence2: Humans are made up of trillions of cells.
[A]: cells


[Q]: Sentence1: Most hormones are regulated by feedback mechanisms. 
Sentence2: Animals regulate hormone release through positive feedback.
[A]:
feedback