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: Streams may start with runoff or water seeping out of a spring. 
Sentence2: Most water comes from precipitation.
Example Output: water

Example Input: Sentence1: lightning can cause a forest fire. 
Sentence2: Lightning can cause a natural cycle in forests.
Example Output: lightning

Example Input: Sentence1: Jaws also make cartilaginous fish excellent predators. 
Sentence2: Jaws make sharks excellent predators.
Example Output:
Jaws