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: Chordates have a complete digestive system and a closed circulatory system. 
Sentence2: All chordates are vertebrates.
Example Output: Chordates

Example Input: Sentence1: Sperm pass out of the body through the urethra. 
Sentence2: Sperm travel from the testicles through the vas deferens to the seminal vesicles and the prostate.
Example Output: Sperm

Example Input: Sentence1: Sweat is released from sweat glands beneath the skin, and as it evaporates, the skin is cooled. 
Sentence2: skin is cooled by evaporation.
Example Output:
evaporates