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.

Input: Consider Input: Sentence1: a stopwatch is used to measure time. 
Sentence2: Time can be measured with a clock or watch.

Output: measure


Input: Consider Input: Sentence1: Animals can communicate with sounds, chemicals, or visual cues. 
Sentence2: cats can communicate with sounds, chemicals or visual cues.

Output: chemicals


Input: Consider Input: Sentence1: Playing is just one of many ways that mammals and other animals learn how to behave. 
Sentence2: Learning and memory are essential to an animal's ability to survive and thrive.


Output: learn