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: Streams may start with runoff or water seeping out of a spring. 
Sentence2: Most water comes from precipitation.
[A]: water


[Q]: Sentence1: Marine species live mainly in shallow coastal waters. 
Sentence2: marine species live mainly in warm waters.
[A]:
Marine