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: Generally, pheromones are volatile substances. 
Sentence2: Male dogs use volatile substances in urine to mark their territory.

SOLUTION: substances

PROBLEM: Sentence1: a circle graph can be used to display percents. 
Sentence2: pie charts are circle graphs.

SOLUTION: circle

PROBLEM: Sentence1: Most people can survive only a few days without water. 
Sentence2: Water is everywhere H20.

SOLUTION:
water