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.

[EX Q]: Sentence1: Finally, the fluid in the nephron reaches a collecting duct . 
Sentence2: fluid in the kidneys collect into ducts.
[EX A]: fluid

[EX Q]: 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.
[EX A]: Sperm

[EX Q]: Sentence1: Evolution occurs by a process called natural selection. 
Sentence2: Adaptation is the result of natural selection.
[EX A]:
natural