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.

Ex Input:
Sentence1: All frogs are amphibians. 
Sentence2: frogs have permeable skin that easily absorbs substances from the environment.

Ex Output:
frogs


Ex Input:
Sentence1: Complex chemistry is needed to carry out all the functions of life. 
Sentence2: Chemistry is primarily concerned with matter, energy, and their interactions.

Ex Output:
chemistry


Ex Input:
Sentence1: electrical current running through a wire causes that wire to heat up. 
Sentence2: resistance in a circuit causes heat.

Ex Output:

heat