Then according to you, everything (except water) is a poison?
I saw that you went back and added a post where you admitted to trolling, but I don't think you are.
I think you just may want to think about what the science of toxicology teaches about level of toxicity, as opposed to the unscientific term "poison".
OK, lets be more scientific about it then. Like I said before I worked in a research lab for the last 13 years. My former boss teaches toxicology. Like in every toxicology class, the opening is usually the dreaded "Dose makes the poison" statement along with a history of Paracelsus and all that jazz. A main point of the class is exactly what you are saying about everything being a poison and so on.
Things start to change when you actually do research and get beyond basic education. Toxicology 101 has very little to do with the real world. To treat everything as a potentially toxic substance makes absolutely no practical sense, in a lab or in real life. One thing we do in research is to classify things by their danger to living organisms in the setting the exposure happens. That's why for example a tank with pure oxygen is classified as dangerous (I know, not a scientific term, but just go with it) but the air around us is not. Nicotine in its pure form, as you would encounter it in a laboratory, would be considered extremely toxic; but we can buy liquid with 36 mg/ml at almost every street corner these days. The reason air and e-liquid are considered non toxic is because in the setting in which we encounter them (as O2 and nicotine), they are non toxic. But that does not make the chemicals themselves non-toxic, only the circumstance.
Another very common method of classification is the chemical properties of a substance. I eluded to that earlier. Warfarin for example is a chemical that has one purpose, and one only.
Wikipedia: Warfarin inhibits the vitamin K-dependent synthesis of biologically active forms of the calcium-dependent clotting factors II, VII, IX and X, as well as the regulatory factors protein C, protein S, and protein Z
In low doses it has the benefit of preventing blood clots. In high doses it will lead to hemorrhage. Regardless of the dose, every single molecule will still have the same toxic effect. That makes its toxic property dose independent. The toxic effect on the human body as a whole is, of course, dose dependent. In other words the biochemical effect is toxic and independent of dose, the physiological effect is toxic and dose dependent.
Same is true for nicotine:
Wikipedia: Nicotine stimulates the release of many chemical messengers such as acetylcholine, norepinephrine, epinephrine, vasopressin, histamine, arginine, serotonin, dopamine, autocrine agents, and beta-endorphin
The difference in Biochemical and Physiological properties are the same as above in the example of Warfarin.
Now, substances like water, molecular nitrogen (N2), calcium, magnesium, most types of monomeric sugars or sugar as polymers (cellulose) work very differently. They do not have a toxic effect on the single molecular (or Biochemical) level. They do not disrupt any pathways or essential function of living organisms. Of course they can be ingested is such a high dose that they become toxic on a physiological level. But by default, ingested in a reasonable, normal physiological manner they are non-toxic, on both the Biochemical and physiological level.
I hope you see now that saying that everything is a poison is a simplified, dangerous, impractical (in real life and science) and truly a 500 year old misconception.
The difference for me is that nicotine (as warfarin) is, first not essential to the body, and second dose independently toxic on the biochemical level. Therefore, in common nonscientific terms, poison. Water is essential and only toxic in insane doses on only the physiological level. Hence not poison.