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: a light bulb is used for seeing in the dark. 
Sentence2: Conventional light bulbs generate light by heating a filament.
bulb

Sentence1: Animals can communicate with sounds, chemicals, or visual cues. 
Sentence2: cats can communicate with sounds, chemicals or visual cues.
chemicals

Sentence1: Viruses are not cells at all, so they are neither prokaryotes nor eukaryotes. 
Sentence2: The smallest agents of disease are not cells at all, so they are neither prokaryotes nor eukaryotes.

cells