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.

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

Example Input: Sentence1: Interestingly, a squid is also a mollusk.
Sentence2: squids have a circulatory system with one or two hearts that pump blood.
Example Output: squid

Example Input: Sentence1: Mutations may change the structure of a chromosome or just change a single nucleotide.
Sentence2: Most mutations are beneficial to the organism.
Example Output:
Mutations