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.

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


[Q]: Sentence1: plant requires seed dispersal for reproduction. 
Sentence2: plants are pollinated by birds.
[A]: plant


[Q]: Sentence1: high pressure systems cause clear weather. 
Sentence2: Bermuda high-pressure systems are a frequent summer visitor.
[A]:
high