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: dew is formed when water vapor condenses over night. 
Sentence2: dew is formed when cooling  over night.
Example Output: dew

Example Input: Sentence1: For example, insulin is a protein hormone. 
Sentence2: Insulin is produced in a part of the cell called the ribosome.
Example Output: insulin

Example Input: Sentence1: Also pyrite within the altered wall rock is oxidized to limonite, geothite and hematite. 
Sentence2: chemical weathering causes pyrite to change to limonite, geothite and hematite.
Example Output:
geothite