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: skin is used for protecting the body from harmful substances. 
Sentence2: Acids are harmful to tissue.
Example Output: harmful

Example Input: Sentence1: Germination depends on the seed coat. 
Sentence2: the force of water causes germination with the emergence of a root.
Example Output: Germination

Example Input: Sentence1: Arthropods are the largest group of animals. 
Sentence2: The largest group of animals are insects.
Example Output:
animals