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.

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.

A: Sperm
****
Q: Sentence1: a light bulb is used for seeing in the dark. 
Sentence2: Conventional light bulbs generate light by heating a filament.

A: bulb
****
Q: Sentence1: measuring the hardness of minerals requires scratching those materials. 
Sentence2: measuring gem hardness requires scratching them.

A:
hardness
****