instruction:
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.
question:
Sentence1: a rainbow is formed by refraction of light by separating light into all different colors. 
Sentence2: Rainbows form when raindrops refract sunlight.
answer:
refraction


question:
Sentence1: Eggs are usually laid in a nest. 
Sentence2: birds have nests.
answer:
nest


question:
Sentence1: Water is essential for all life on Earth. 
Sentence2: H2O is needed for all life on Eartth.
answer:

Earth