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: Similarly, stars are referred to as suns, but our star is the Sun. 
Sentence2: our star causes water to evaporate more quickly by adding heat.

Ex Output:
our


Ex Input:
Sentence1: Silica sand is primarily mined from sandstone deposits. 
Sentence2: erosion forms silica sand.

Ex Output:
Silica


Ex Input:
Sentence1: magnetism can cause objects to repel each other. 
Sentence2: a spinning electron can cause objects to repel each other.

Ex Output:

cause