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: Blood type is important for medical reasons. 
Sentence2: Type O is important for medical reasons.
Example Output: important

Example Input: Sentence1: dew is formed when water vapor condenses over night. 
Sentence2: Condensing is a gas turning into a liquid.
Example Output: condenses

Example Input: Sentence1: when a metal rusts , that metal becomes orange on the surface. 
Sentence2: Yin metal is small metal, jewelery metal and decorative metal.
Example Output:
metal