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: Sound vibrations travel at different speeds through different materials. 
Sentence2: the type of material through which sound passes changes the sound vibrations.
Example Output: Sound

Example Input: Sentence1: Minerals are chemical elements that are essential for body processes. 
Sentence2: minerals are needed by body processes.
Example Output: processes

Example Input: Sentence1: Chemistry is primarily concerned with matter, energy, and their interactions. 
Sentence2: the functions of life require energy.
Example Output:
energy