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 sifter is used for separating mixtures. 
Sentence2: a sifter is used for some recipes.
[EX A]: sifter

[EX Q]: Sentence1: Fractures heal when osteoclasts form new bone. 
Sentence2: Fractures A fracture is a broken or cracked bone.
[EX A]: Fractures

[EX Q]: Sentence1: living things all require energy for survival. 
Sentence2: Living things all require energy for reproduction.
[EX A]:
living