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: an image in a mirror is formed by reflecting light. 
Sentence2: mirrors can be seen with our eyes.

Ex Output:
mirror


Ex Input:
Sentence1: Sweat glands produce more sweat. 
Sentence2: When the body is hot, something coming from a gland is produced to cool the body.

Ex Output:
glands


Ex Input:
Sentence1: Many zooplankton are crustaceans. 
Sentence2: tiny crustaceans can feed on phytoplankton.

Ex Output:

crustaceans