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.

Example Input: Sentence1: a light bulb is used for seeing in the dark. 
Sentence2: light is required for seeing.
Example Output: seeing

Example Input: Sentence1: evaporation can be used for separating a solute from a solvent in a solution. 
Sentence2: Evaporation can be used for segregation a solute from a solvent in a solution.
Example Output: a

Example Input: Sentence1: claws are used to catch prey by some predators. 
Sentence2: Birds have beaks and claws.
Example Output:
claws