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: waxy leaves are used for storing water by some plants. 
Sentence2: waxy leaves are used for water conservation by some plants.
[A]: leaves


[Q]: Sentence1: Bacteria and Viruses Bacteria and viruses can cause diseases. 
Sentence2: bacteria can have a negative impact on an organism.
[A]: Bacteria


[Q]: Sentence1: Antigens are molecules that the immune system recognizes as foreign to the body. 
Sentence2: When the immune system recognizes a foreign substance, antibodies are produced.
[A]:
foreign