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: moss causes chemical weathering. 
Sentence2: If the moss was completely dried then it is dead.
Example Output: moss

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: For that, the player needs lumberjacks to cut down the trees. 
Sentence2: Creating wood-free paper does not require lumberjacks.
Example Output:
lumberjacks

