Bitcoin is a worldwide cryptocurrency and digital payment system[9] called the first decentralized digital currency, as the system works without a central repository or single administrator.[9]:1[10] It was invented by an unknown programmer, or a group of programmers, under the name Satoshi Nakamoto[11] and released as open-source software in 2009.[12] The system is peer-to-peer, and transactions take place between users directly, without an intermediary.[9]:4 These transactions are verified by network nodes and recorded in a public distributed ledger called a blockchain.
Bitcoins are created as a reward for mining. They can be exchanged for other currencies,[13] products, and services. As of February 2015, over 100,000 merchants and vendors accepted bitcoin as payment.[14] Bitcoin can also be held as an investment. According to research produced by Cambridge University in 2017, there are 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin.
The word bitcoin occurred in the white paper[16] that defined bitcoin published on 31 October 2008.[17] It is a compound of the words bit and coin.[18] The white paper frequently uses the shorter coin.[16]
There is no uniform convention for bitcoin capitalization. Some sources use Bitcoin, capitalized, to refer to the technology and network and bitcoin, lowercase, to refer to the unit of account.[19] The Wall Street Journal,[20] The Chronicle of Higher Education,[21] and the Oxford English Dictionary[18] advocate use of lowercase bitcoin in all cases, a convention which this article follows.
Units[edit]
The unit of account of the bitcoin system is bitcoin. As of 2014, symbols used to represent bitcoin are BTC,[a] XBT,[b] and ₿.[26]:2 Small amounts of bitcoin used as alternative units are millibitcoin (mBTC),[1] microbitcoin (µBTC, sometimes referred to as bit), and satoshi. Named in homage to bitcoin's creator, a satoshi is the smallest amount within bitcoin representing 0.00000001 bitcoin, one hundred millionth of a bitcoin.[5] A millibitcoin equals to 0.001 bitcoin, one thousandth of a bitcoin.[27] One microbitcoin equals to 0.000001 bitcoin, one millionth of a bitcoin.