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: If there is no movement friction is zero. 
Sentence2: Movement causes the temperature of an object to increase.

Ex Output:
movement


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: burning wood is used to produce heat. 
Sentence2: wood has to be cut to be used in a stove.

Ex Output:

wood