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.

Ex Input:
Sentence1: Roundworms make up the phylum Nematoda. 
Sentence2: Also, nematoda and rotifera are important groups contributing to soils.

Ex Output:
Nematoda


Ex Input:
Sentence1: First, the bottle is calibrated with a graduated cylinder. 
Sentence2: calibration is performed with a cylinder.

Ex Output:
calibrated


Ex Input:
Sentence1: gases released during the use of fossil fuels causes global warming. 
Sentence2: Adoption of geothermal energy to produce electricity can reduce global warming.

Ex Output:

global