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: Most pituitary hormones control other endocrine glands. 
Sentence2: Hormones tell the ovaries to produce eggs.
[A]: hormones


[Q]: Sentence1: Tree-ring dating the 1700 Cascadia earthquake. 
Sentence2: estimating the age of trees can be used in reviewing earthquake history.
[A]: earthquake


[Q]: Sentence1: plasma is formed by electrons separating from atoms in stars. 
Sentence2: interstellar space contains electrons, atoms, and stars.
[A]:
atoms