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: Energy enters ecosystems in the form of sunlight or chemical compounds. 
Sentence2: Energy enters ecosystems in the form of photons.
[A]: Energy


[Q]: Sentence1: the ovaries are used in reproduction. 
Sentence2: Unlike most female animals, which have two functioning ovaries, the chicken usually has only one.
[A]: ovaries


[Q]: Sentence1: Aerosols are tiny particles suspended in the air. 
Sentence2: a breathing mask is used for keeping aerosols from entering the respiratory system.
[A]:
Aerosols