TASK DEFINITION: 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.
PROBLEM: 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.

SOLUTION: pheromones

PROBLEM: Sentence1: Nonmetal elements are far fewer in number. 
Sentence2: There are 17 nonmetals on the periodic table.

SOLUTION: Nonmetal

PROBLEM: Sentence1: Present day erosion is caused by wind. 
Sentence2: Uneven heating of the Earth's surface can cause erosion.

SOLUTION:
erosion