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: Temperature Scales Temperature is the energy of vibration. 
Sentence2: a thermometer is used to measure energy of vibration.
[A]: energy


[Q]: Sentence1: Cell death occurs by activation of cell death genes. 
Sentence2: Aging is associated with the activation of certain genes.
[A]: activation


[Q]: Sentence1: Earthworms crawl through the soil, eating sediments or dirt directly. 
Sentence2: Earthworms eat dirt, which is good for plants.
[A]:
dirt