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.
Information on Patents for Researchers. A patent is a legal title granting an inventor the right to exclude others from making, using or selling the claimed invention. The duration of a patent in the U.S.A is 20 years from the date of filing. A patent may be granted for any new and useful process, machine, manufacture or composition of matter, or any new and useful improvements thereof.