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 property right to a product and in the case of pharmaceutical companies is usually in the form of a chemical formula that may not be duplicated by any rival company. The life of a patent is 20 years from the time the patent is issued. patent is a property right to a product and in the case of pharmaceutical companies is usually in the form of a chemical formula that may not be duplicated by any rival company. The life of a patent is 20 years from the time the patent is issued.