Dollar sign meaning and origin
The dollar sign $ marks amounts in US dollars and in dozens of other currencies called dollars, from the Canadian and Australian dollar to the Hong Kong and Singapore dollar. Mexico, Chile, Colombia and several other countries use the same sign for their pesos.
The most widely accepted theory is that $ grew out of "ps", the abbreviation for Spanish pesos, written quickly in 18th-century handwriting until the s ran over the p. Some fonts draw the sign with two vertical strokes instead of one. Unicode treats both as the same character, so there is no separate double-stroke dollar to copy; which version you see depends on the font.
Beyond money, $ is busy in computing: PHP variables and shell variables start with $ ($HOME), and in Excel $A$1 is an absolute cell reference. In LaTeX, $ starts math mode, so you type \$ to print a dollar sign.
How to write dollar amounts
In American English, put $ before the number with no space: $5, $19.99, $1,250. For big round numbers, write $2 million or $2.5 billion, and in casual writing $5K or $1M. If readers might confuse dollars, add the country, as in US$100, CA$100 or A$100, or use the ISO code: USD 100.
In Canadian French, the sign follows the number with a space and a decimal comma: 19,99 $. Prices under a dollar can use the cent symbol, as in 99¢, but do not combine $ and ¢ in one price.
How to type $ and dollar emoji
On US and UK keyboards, $ is Shift + 4, and in HTML you can write $. The fullwidth ＄ is meant for Chinese, Japanese and Korean text, where it matches the width of the surrounding characters, and ﹩ is a small form variant.
💲 (heavy dollar sign) and 💵 (dollar banknote) are emoji, so they show in color and look a little different on every platform. Find them by searching "dollar" in your phone's emoji keyboard, or press Windows + . on a PC. Signs for other money, like the euro and the pound, are on the currency symbols page.