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: Any antigen that causes an allergy is called an allergen. 
Sentence2: molds are antigens.

Ex Output:
antigen


Ex Input:
Sentence1: if an object is made of a material then that object has the properties of that material. 
Sentence2: items properties are the same as the materials the item is made of.

Ex Output:
made


Ex Input:
Sentence1: Cnidarians are invertebrates such as jellyfish and corals. 
Sentence2: Cnidarians are entirely aquatic animals.

Ex Output:

Cnidarians