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: Ovulation is the release of an egg from an ovary. 
Sentence2: The release of an egg during ovulation is used in reproduction.
[EX A]: Ovulation

[EX Q]: Sentence1: a tape measure is used to measure length. 
Sentence2: Length The Base unit for length in the metric system is the meter .
[EX A]: length

[EX Q]: Sentence1: a car engine usually converts gasoline into motion and heat through combustion. 
Sentence2: Car engines convert gasoline into friction.
[EX A]:
car