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: Mammals depend on the vegetation for food and shelter. 
Sentence2: Mammals are Heterotrophs.
Example Output: Mammals

Example Input: Sentence1: Cnidarians are invertebrates such as jellyfish and corals. 
Sentence2: Jellyfish and corals are radial, tentacled animals that live mostly in the seas.
Example Output: corals

Example Input: Sentence1: if all members of a species cannot produce offspring then that species will likely become extinct. 
Sentence2: Extinct animals include the dodo bird and the saber-toothed tiger.
Example Output:
extinct