Since the discourse community itself is intangible, it is easier to imagine discourse communities in terms of the fora in which they operate. The hypothetical journal and email list can each be seen as an example of a forum, or a concrete, local manifestation of the operation of the discourse community.
Daily nausea can be caused by stress. An ulcer in the small intestine may cause chronic nausea. Excessive consumption of caffeine can cause nausea. A person may develop chronic nausea in relation to a peptic ulcer. Indigestion is one of the most common causes of nausea.
After the first few months of life, the most common cause of vomiting is a stomach or intestinal infection. Viruses are by far the most frequent infecting agents, but occasionally bacteria and even parasites may be the cause. The infection also may produce fever, diarrhea, and sometimes nausea and abdominal pain.