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: Organisms cluster around hydrothermal vents in the ocean floor. 
Sentence2: vents on the ocean floor are powered by heat.
vents

Sentence1: friction is used for stopping a vehicle by brakes. 
Sentence2: friction is used for stopping a car by brakes.
brakes

Sentence1: Echinoderms lack respiratory and excretory systems. 
Sentence2: Echinoderms are represented by the starfish.

Echinoderms