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: Finally, the fluid in the nephron reaches a collecting duct . 
Sentence2: fluid in the kidneys collect into ducts.
fluid

Sentence1: Viruses contain DNA but not much else. 
Sentence2: viruses contain encoded information but not much else.
Viruses

Sentence1: the type of material through which sound passes changes the speed at which sound travels. 
Sentence2: the type of material through which waves passes changes the speed at which waves move.

changes