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 Q]: Sentence1: Flatworms Flatworms or Platyhelminthes include flukes, tapeworms, and turbellarians. 
Sentence2: Tapeworms belong to the phylum Platyhelminthes.
[EX A]: tapeworms

[EX Q]: Sentence1: Any antigen that causes an allergy is called an allergen. 
Sentence2: molds are antigens.
[EX A]: antigen

[EX Q]: Sentence1: Genes and chromosomes exist in pairs. 
Sentence2: genes on the same pair are linked.
[EX A]:
pairs