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: protein is used to repair cells by the human body. 
Sentence2: Wound healing requires protein.
protein

Sentence1: Heterotrophs are living things that cannot make their own food. 
Sentence2: food contains organic molecules.
food

Sentence1: boiling is when liquids are heated above their boiling point. 
Sentence2: Vapor pressure is about liquids boiling.

boiling