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: Moisture is required for the microorganisms to grow. 
Sentence2: Moisture can cause infections to grow.
[A]: Moisture


[Q]: Sentence1: cold fronts cause thunderstorms as they pass by. 
Sentence2: Cold fronts cause lightning.
[A]: cold


[Q]: Sentence1: a rainbow is formed by refraction of light by separating light into all different colors. 
Sentence2: When the light waves strike a prism, the rays of light refract, or bend, at different angles.
[A]:
light