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: a stopwatch is used to measure time. 
Sentence2: Time can be measured with a clock or watch.
[EX A]: measure

[EX Q]: Sentence1: Fertilization occurs naturally in the fallopian tubes. 
Sentence2: fertilization is used for reproduction.
[EX A]: Fertilization

[EX Q]: Sentence1: tidal energy can be used to produce electricity. 
Sentence2: Tidal caves are formed by the energy of the rising and falling tides.
[EX A]:
tidal