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

Example Input: Sentence1: Interest in fossils is worldwide. 
Sentence2: paleontologists study something with worldwide interest.
Example Output: Interest

Example Input: Sentence1: Sunlight is energy released from fusion reactions in the sun. 
Sentence2: photosynthesis requires energy from the sun.
Example Output:
sun