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: hearing is used for sensing sound by animals. 
Sentence2: functioning ears are used for sensing sound by animals.

A: animals
****
Q: Sentence1: Most major Atlantic hurricanes start as small disturbances moving westward off Africa. 
Sentence2: When something that starts as a small disturbance moving westward off Africa then moves over land, it will decrease in strength.

A: Africa
****
Q: Sentence1: smoking causes direct damage to the lungs. 
Sentence2: Mammals are warm blooded, use lungs for respiration, and have four legs.

A:
lungs
****