instruction:
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.
question:
Sentence1: a light bulb is used for seeing in the dark. 
Sentence2: Conventional light bulbs generate light by heating a filament.
answer:
bulb


question:
Sentence1: lightning can cause a forest fire. 
Sentence2: Lightning can cause a natural cycle in forests.
answer:
lightning


question:
Sentence1: tidal energy can be used to produce electricity. 
Sentence2: Tidal energy is one of the oldest forms of energy used by humans.
answer:

tidal