instruction:
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.
question:
Sentence1: Mammalian teeth are important for digestion. 
Sentence2: bats' teeth are important for digestion.
answer:
digestion


question:
Sentence1: Sound vibrations travel at different speeds through different materials. 
Sentence2: the type of material through which sound passes changes the sound vibrations.
answer:
Sound


question:
Sentence1: the moon revolving around the Earth causes the phases of the moon. 
Sentence2: Lets start our discussion of the Moon's phases with the New Moon phase.
answer:

phases