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: soil is formed by weathering. 
Sentence2: Something described as loamy is formed by weathering.
Example Output: formed

Example Input: Sentence1: June Summer Triangle Three bright stars light up the summer sky. 
Sentence2: Nuclear reactions in stars cause them to brighten up the summer sky.
Example Output: bright

Example Input: Sentence1: a stopwatch is used to measure time. 
Sentence2: a stopwatch is used to measure seconds.
Example Output:
a