The satoshi is the smallest unit of the bitcoin cryptocurrency. It is named after Satoshi Nakamoto, the creator of the protocol used in blockchains and the bitcoin cryptocurrency. The satoshi to bitcoin ratio is 100 million satoshis to one bitcoin.
Unlike the physical versions of global currencies, such as the British pound or U.S. dollar, cryptocurrencies predominately exist in the digital world. Despite this difference, a cryptocurrency can be divided into smaller units, just as the pound is broken into pence and the dollar into cents. In the case of bitcoins, the smallest unit available is called the satoshi.
The satoshi unit is named after Satoshi Nakamoto, the anonymous person (or persons) that published a white paper in 2008 that jumpstarted the development of the bitcoin cryptocurrency. The paper, "Bitcoin: A Peer-to-Peer Electronic Cash System", described the use of a peer-to-peer network as a solution to the problem of double-spending. The problem—that a digital currency or token can be used in more than one transaction—is not found in physical currencies, as a physical bill or coin can, by its nature, only exist in one place at a single time. Since digital currency does not exist in the physical space, using it in a transaction does not remove it from someone's possession.
The satoshi represents one hundred millionths of a bitcoin. Small denominations make bitcoin transactions easier to conduct and makes extremely fine transactions readable. The general unit structure of bitcoins has 1 bitcoin equivalent to 1,000 millibitcoins (mBTC), 1,000,000 microbitcoins (μBTC), or 100,000,000 satoshis. While the exact figure is unknown, it is estimated that Satoshi Nakamoto may possess 1 million bitcoins, equivalent to 100,000,000,000,000 satoshis.