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.
The timing of the nausea or vomiting can indicate the cause. When appearing shortly after a meal, nausea or vomiting may be caused by food poisoning, gastritis (inflammation of the stomach lining), an ulcer, or bulimia. Nausea or vomiting one to eight hours after a meal may also indicate food poisoning. However, certain food-borne bacteria, such as salmonella, can take longer to produce symptoms.