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

Sentence1: a light bulb is used for seeing in the dark. 
Sentence2: light is required for seeing.
seeing

Sentence1: People understand that habitat destruction and pollution are harmful to wildlife. 
Sentence2: pollution has a negative impact on the population size of a species.

pollution