Bitcoin is a cryptocurrency and a digital payment system:3 invented by an unknown programmer, or a group of programmers, under the name Satoshi Nakamoto. It was released as open-source software in 2009.
The system is peer-to-peer, and transactions take place between users directly, without an intermediary.:4 These transactions are verified by network nodes and recorded in a public distributed ledger called the blockchain. Since the system works without a central repository or single administrator, bitcoin is called the first decentralized digital currency.
As of February 2015, over 100,000 merchants and vendors accept bitcoin as payment. According to a research produced by Cambridge University in 2017, there are 2.9 to 5.8 million unique users actively using a cryptocurrency wallet, most of them using bitcoin.
Etymology and orthography
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. The Wall Street Journal, The Chronicle of Higher Education, and the Oxford English Dictionary advocate use of lowercase bitcoin in all cases, which this article follows.