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 means a property right granted by a government agency. A land patent is an official recognition of a claim to a defined piece of real estate. An invention patent is an official recognition of a claim to an invention. It does NOT grant any inherent rights: it grants the right to exclude OTHERS from making, using, selling or importing the claimed invention for the duration of the patent validity. If the patent uses inventions that are claimed by others, the later patent holder must still obtain a license to make, use, sell or import that portion of the patented invention that is still under valid patents owned by others.