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: Cells are the units of function in living things. 
Sentence2: living things cannot survive without oxygen.
Example Output: living

Example Input: Sentence1: Visible and invisible light is energy in the form of electromagnetic waves. 
Sentence2: Eyes are used for seeing animals by sensing electromagnetic waves.
Example Output: electromagnetic

Example Input: Sentence1: Gene cloning is the process of isolating and making copies of a gene. 
Sentence2: cloning allows us to make copies of traits.
Example Output:
cloning