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.

Sentence1: Muscles can only contract. 
Sentence2: Contraction is a type of movement.
contract

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

Sentence1: RNA is a small molecule that can squeeze through pores in the nuclear membrane. 
Sentence2: polymers of various small chemically related molecules can squeeze through pores in the nuclear membrane.

membrane