Libra pondo is a historical unit of mass in the Roman Republic and later the Roman Empire, derived from the Latin for "pound by weight". The original ancient Roman unit was the libra (the origin of the English word "pound"), weighing approximately 327 grams. During the Middle Ages, "pound" came into use, representing different amounts of weight depending on location and commodity, and other "pounds" or variations began to be defined by weight versus troy weight, used when weighing gold and silver.