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: Faster metabolism means more calories consumed, and usually, weight loss. 
Sentence2: mammals generate heat by consuming calories.

A: calories
****
Q: Sentence1: Cells are the units of function in living things. 
Sentence2: living things cannot survive without oxygen.

A: living
****
Q: Sentence1: an automobile engine transforms chemical energy into mechanical energy. 
Sentence2: Automobile engines transform chemical energy into energy of moving objects.

A:
automobile
****