Hello, I am finding different types of definitions for the word "pathogen" on the internet and I am not sure which one is correct (or more correct). At most places, the word is defined as a "An organism that causes disease in another organism" others as "turn of events that leads to a disease disease manifestation followed by harmful effect". However, tracing the etymology of the word gives results that are more related to the second definition. So is pathogen strickly disease causing microorgansim (or ~small organism) or is there such a thing as chemical pathogen like nervgas or poisonous chemicals? Thank you for your time. Have a nice day.