A pound sign can refer to two very different symbols, depending on what country a person using the term is in or from. In the UK, for example, this sign refers to the “£” symbol that is typically used to indicate the standard monetary units of England, also called a “pound.” This is essentially a stylized letter “L” with a horizontal line through it to indicate that it is a symbol and not meant as an actual letter. A pound sign in the US, however, usually indicates the “#” symbol, which is often referred to as a “hash mark” or “number sign” in other countries.
There are two very different potential meanings that someone can be trying to express when he or she refers to a “pound sign,” based on where that person is from. One of the most common uses of this term is to refer to the British pound sign, which appears as “£” and usually denotes English money. This symbol derives from a slightly stylized upper case letter “L,” which stems from the word libra to refer to old forms of currency. This is the Latin word for a particular unit of weight, and stems from the way in which British currency was once valued.
British currency is referred to as “pounds” and uses the pound sign because it was initially valued by comparison to a certain quantity of silver. A single “Tower pound,” which was an older measurement of weight in England, of silver was the value of one unit of currency, hence the name “pound.” This use of weight to determine value is connected to the concept of the libra and the “£” symbol that become used as the pound sign. The common abbreviation for pound as “lb” also stems from the word libra.
This abbreviation for a pound, “lb,” has been used in numerous countries, including the US. At one point, it was indicated with a horizontal strike through it in the US to differentiate it from other letters, and eventually this was replaced by a symbol similar to “#,” which was easier to read. This led to the “#” symbol becoming referred to as a pound sign in American English, though other countries do not refer to it as such, instead using the terms “hash mark” or “number sign.” Early word processing software often did not have a symbol for the “£” mark, but the “#” could be used instead with a utility that had the printer create the “£” instead of printing out a “#,” further adding to the confusing, interchangeable usage for many Americans.