The position of the medical and scientific communities is that nicotine is most definitely addictive. A good example would be someone who continues to smoke, even as they use an oxygen tank to breathe because of the damage smoking has done to their lungs.
Neuroscientists call anything that turns on the reward pathway in the brain addictive.
Because stimulating this neural circuitry makes you feel so good, you will continue to do it again and again to get those feelings back. Nicotine's effects are short-lived, lasting only 40 minutes to a couple of hours. This leads people to smoke or chew tobacco periodically throughout the day to dose themselves with nicotine. While you're using nicotine-containing products, your body adapts the way it works to compensate for the effects of the nicotine. For example, neurons in your brain might increase or decrease the number of receptors or the amount of different neurotransmitters affected by the presence of nicotine.