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 greenhouse is used to protect plants by keeping them warm. 
Sentence2: Flower size varies by plant.
Example Output: plants

Example Input: Sentence1: Blood is a fluid connective tissue. 
Sentence2: A fluid connective tissue carries oxygen to the brain.
Example Output: connective

Example Input: Sentence1: Bryophytes depend on moisture to reproduce. 
Sentence2: Mosses are the most common bryophytes.
Example Output:
Bryophytes