TASK DEFINITION: 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.
PROBLEM: Sentence1: Limestone caves displaying stalactites. 
Sentence2: Limestone caves are formed by depositions.

SOLUTION: Limestone

PROBLEM: Sentence1: Introns are regions that do not code for proteins. 
Sentence2: regions that do not code for proteins are removed by RNA splicing.

SOLUTION: code

PROBLEM: Sentence1: a rainbow is formed by refraction of light by separating light into all different colors. 
Sentence2: Water vapor bends the light.

SOLUTION:
light