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: Chromosomes are the form of the genetic material of a cell during cell division. 
Sentence2: Microtubules move the genetic material of a cell during cell division.
Example Output: cell

Example Input: Sentence1: Conventional myosin is required for cytokinesis . 
Sentence2: Conventional myosin is required for the final stage of cell division.
Example Output: Conventional

Example Input: Sentence1: Natural selection is the mechanism of evolution. 
Sentence2: Mutations allow for natural selection to occur.
Example Output:
Natural