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: a plant requires sunlight to grow. 
Sentence2: Grass needs air and sunlight.
[EX A]: sunlight

[EX Q]: Sentence1: Antigens are proteins foreign to the body. 
Sentence2: antigens are proteins.
[EX A]: proteins

[EX Q]: Sentence1: Recyclability and recycling of materials is essential. 
Sentence2: It is essential to reduce resources needed to make things.
[EX A]:
essential