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.

Sentence1: Most water comes from precipitation. 
Sentence2: aquatic animals require precipitation to survive.
precipitation

Sentence1: Finally, the fluid in the nephron reaches a collecting duct . 
Sentence2: fluid in the kidneys collect into ducts.
fluid

Sentence1: killing microorganisms in food can be used to extend the shelf life of that food. 
Sentence2: irradiation can be used to extend the shelf life of food.

extend