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: Basically the process is pretty simple. 
Sentence2: All cells share some of the same structures and simple processes.
Example Output: process

Example Input: Sentence1: Homogeneous mixtures are called solutions. 
Sentence2: A homogenous mixture is formed when one substance dissolves in another.
Example Output: Homogeneous

Example Input: Sentence1: Mammals generate heat mainly by keeping their metabolic rate high. 
Sentence2: Birds have a high metabolic rate and a high energy requirement.
Example Output:
metabolic