Mammoth Cave, the world's longest known cave system. The following is a list of the world's 10 longest caves per length of documented passageways. Many passageways are still being discovered; this list is based on the latest verifiable data.
patent medicine - medicine that is protected by a patent and available without a doctor's prescription. medicament, medication, medicinal drug, medicine - (medicine) something that treats or prevents or alleviates the symptoms of disease. nostrum - patent medicine whose efficacy is questionable.
A patent is a governmental grant of a short-term monopoly to inventors. U.S. patent laws enable a patent holder to prevent others from making, using or selling the patented invention for a specific time period. How long a patent remains valid depends on the type of patent and other factors. A patent is a governmental grant of a short-term monopoly to inventors. U.S. patent laws enable a patent holder to prevent others from making, using or selling the patented invention for a specific time period.