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: if an object is black then that object absorbs all visible light. 
Sentence2: Something is black if it absorbs visible light and doesn't reflect.
[A]: light


[Q]: Sentence1: smell is used for finding food by some animals. 
Sentence2: Food includes small rodents and birds.
[A]: food


[Q]: Sentence1: Shivering costs the bird, however, by depleting energy stores. 
Sentence2: mammals can generate heat by depleting energy stores.
[A]:
depleting