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: Balance is the ability to sense and maintain body position. 
Sentence2: Another part of the inner ear is used for balance.
Balance

Sentence1: keeping food cold is used for keeping food fresh. 
Sentence2: Keeping food at 40 degrees F or lower is used for keeping food fresh.
food

Sentence1: Every frog starts as a tadpole. 
Sentence2: skin is used for breathing air by tadpoles.

tadpole