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: Mammalian teeth are important for digestion. 
Sentence2: bats' teeth are important for digestion.

A: digestion
****
Q: Sentence1: Metabolic rate is the rate at which food is burned for energy. 
Sentence2: thyroid hormones increase the rate of energy consumption.

A: energy
****
Q: Sentence1: Most water comes from precipitation. 
Sentence2: aquatic animals require precipitation to survive.

A:
precipitation
****