The word bitcoin first occurred and was defined in the white paper^[15] that was published on 31 October 2008.^[16] It is a compound of the words bit and coin.^[17] The white paper frequently uses the shorter coin.^[15]

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.^[18] The Wall Street Journal,^[19] The Chronicle of Higher Education,^[20] and the Oxford English Dictionary^[17] advocate use of lowercase bitcoin in all cases, a convention which this article follows.

Units

The unit of account of the bitcoin system is bitcoin. As of 2014, tickers used to represent bitcoin are BTC^[a] and XBT.^[b] Its Unicode character is ₿.^[25]:2 Small amounts of bitcoin used as alternative units are millibitcoin (mBTC)^[1] 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.^[4] A millibitcoin equals to 0.001 bitcoin, one thousandth of a bitcoin.^[26]