Definition: 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.
Input: Sentence1: If a star has a mass larger than 25 solar masses, it collapses into a black hole. 
Sentence2: Black holes are formed by stars that have mass larger than 25 solar masses.

25