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: Scientists still know relatively little about Archaea. 
Sentence2: scientists still know relatively little about non-bacterial prokaryotes.

A: Scientists
****
Q: Sentence1: Condoms can break; Condoms can be used incorrectly. 
Sentence2: If a condom breaks during sex, there is a risk of both pregnancy and infection.

A:
break
****