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: Nitrogen is found in proteins, nucleic acids, and chlorophyll. 
Sentence2: Nitrogen, as a gas, is colorless, odorless, and a generally inert element.
Example Output: Nitrogen

Example Input: Sentence1: Caverns Secrets are hidden in caves. 
Sentence2: hidden caves are formed by carbonic acid in groundwater seeping through rock and dissolving limestone.
Example Output: are

Example Input: Sentence1: Shrub beds and ground covers require less water and provide more variety to the landscape. 
Sentence2: Shrub beds need less water and will survive in a drought.
Example Output:
Shrub