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: Moisture is required for the microorganisms to grow. 
Sentence2: Moisture can cause infections to grow.
[A]: Moisture


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


[Q]: Sentence1: Fertilization occurs when a sperm and an egg fuse to form a diploid zygote. 
Sentence2: If a human ovum is fertilized, a zygote is formed.
[A]:
Fertilization