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: If there is sun, there is sunlight, there is day. 
Sentence2: Energy enters ecosystems from the sun.
[A]: sun


[Q]: Sentence1: Interestingly, a squid is also a mollusk. 
Sentence2: squids have a circulatory system with one or two hearts that pump blood.
[A]: squid


[Q]: Sentence1: keeping food cold is used for keeping food fresh. 
Sentence2: Keeping food at 40 degrees F or lower is used for keeping food fresh.
[A]:
food