What is "pound sign"

octothorp \oc"to*thorp\, octothorpe \oc"to*thorpe\, n. [octo- eight + thorp Etymology of thorp uncertain. (ca. 1965). See quote below. Possibly derived from octalthorpe or octotherp (once used by the Bell System?).] A typographic symbol (#) having two vertical lines intersected by two horizontal lines. It is also called the crosshatch, hash, numeral sign and number sign; in the U. S. it is commonly called the pound sign, especially to designate the symbol as used on digital telephone dials, but this can be confusing to Europeans who think of the pound sign as the symbol for the British pound. It is commonly used as a symbol for the word number; as in #36 (meaning: number thirty-six).

octothorp Otherwise known as the numeral sign. It has also been used as a symbol for the pound avoirdupois, but this usage is now archaic. In cartography, it is also a symbol for village: eight fields around a central square, and this is the source of its name. Octothorp means eight fields.
--Robert Bringhurst (The Elements of Typographic Style (2d edition, 1996), Hartley & Marks, Publishers, Point Roberts, WA; Vancouver, BC, Canada, p. 282)

n. 1 (context British English) The symbol £ representing the pound sterling. 2 (context US English) The symbol (unsupported: #) on a telephone.

The pound sign (£) is the symbol for the pound sterling—the currency of the United Kingdom (UK). The same symbol is used for similarly named currencies such as the Gibraltar pound or occasionally the Syrian pound. It is also sometimes used for currencies named lira, for example the now withdrawn Italian lira, and on rare occasion, the Turkish lira.

The symbol derives from a capital " L", representing libra, the basic unit of weight in the Roman Empire, which in turn is derived from the Latin name of the same spelling for scales or a balance. The pound became an English unit of weight and was so named because it originally had the value of one tower pound (~350 grams) of fine (pure) silver.

The pound sign is placed before the number (e.g. "£12,000") and separated from the following digits by no space or only a thin space.

The symbol ₤ was called the lira sign in Italy, before the adoption of the euro. It was used as an alternative to the more usual L to show prices in lire. It was also used unofficially as the symbol of the Maltese lira instead of the official Lm.

In American English, the term "pound sign" usually refers to the symbol # (see number sign), and the corresponding telephone key is called the "pound key". The symbols £ and # are both referred to as the pound sign in Canadian English (# is also referred to as the " number sign" and "noughts-and-crosses board").

In the original old Caslon metal fonts, the pound sign was identical to the italic capital " J" rotated 180 degrees.