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: An example of a cartilaginous fish is a shark. 
Sentence2: jaws make sharks excellent predators.
shark

Sentence1: radioactive dating is used to determine the age of fossils. 
Sentence2: For a fossil to be made, the dead plant or animal has to be buried rapidly by sediment.

fossils