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: harming an animal species causes that animal 's population to decrease. 
Sentence2: Oil spill sare harmful to animals and the enviroment.

A: harming
****
Q: Sentence1: camouflage is used for protection by prey against predators. 
Sentence2: blending is used for protection.

A: protection
****
Q: Sentence1: a telescope is used for observing stars by astronomers. 
Sentence2: For instance, the two brightest stars in Orion are Betelgeuse and Rigel.

A:
stars
****