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 flashlight converts chemical energy into light energy. 
Sentence2: Only as long as there are batteries in the flashlight, the flashlight will function.
[EX A]: flashlight

[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: Humans are complex organisms. 
Sentence2: fertilization takes place in human females.
[EX A]:
Humans