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: Most bryophytes are small. 
Sentence2: Most in the same group as mosses are small.
Example Output: small

Example Input: Sentence1: damming a river can cause a lake to form. 
Sentence2: Damming a river can cause water ponding in a depression.
Example Output:
cause