A more thorough explanation:

Definition: Libra (lI-brə) is a term used in history to refer to an English pound, which is a sum of money equal to a pound sterling. It can also refer to different types of pounds, such as libra arsa, which is a pound melted to test its purity, libra numerata, which is a pound of money that has been counted, and libra pensa, which is a pound of money by weight.

• He paid 10 librae for the goods he purchased.
• The libra arsa was used to ensure that the coins were not debased.
• The merchant counted out the libra numerata to pay for the spices.
• The libra pensa was used to weigh the gold coins.

These examples illustrate how the term libra was used in different contexts to refer to a sum of money or a unit of weight. In each case, libra was used to measure the value of something, whether it was a pound of coins, a pound of gold, or a pound of goods. The term was commonly used in medieval times and is still used in some contexts today.