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: Male dogs use pheromones in urine to mark their territory. 
Sentence2: Pheromones are hormones that are thought to stimulate, through smell, sexual reactions in animals.

A: pheromones
****
Q: Sentence1: a light bulb is used for seeing in the dark. 
Sentence2: light is required for seeing.

A: seeing
****
Q: Sentence1: Solvents are substances, usually liquid, that dissolve other substances. 
Sentence2: When one solvent reacts with another, chemical bonds form.

A:
Solvents
****