I'm still unsure when to use Bitcoin and when bitcoin is more appropriate. Did anyone define when to use the word Bitcoin with a capital B? Is one used to talk about the currency as in "3 Bitcoin" and the other for the "bitcoin protocol"?


2 Answers 2


From Introduction on the Bitcoin wiki:

Capitalization / Nomenclature

Since Bitcoin is both a currency and a protocol, capitalization can be confusing. Accepted practice is to use Bitcoin (singular with an upper case letter B) to label the protocol, software, and community, and bitcoins (with a lower case b) to label units of the currency.

So, the accepted usage in your example would be "3 bitcoin" and the "Bitcoin protocol".

  • So "add the bitcoin amount" with small b is correct as we talk about the units of the currency? Thanks.
    – Cimm
    Mar 25, 2014 at 8:54
  • @Greg, So would we say "I have a bitcoin address" or "I have a Bitcoin address"?
    – Pacerier
    Jun 2, 2014 at 9:20
  • @Pacerier: According to the above, that would be "Bitcoin address". Jun 2, 2014 at 16:09

Bitcoin (capital B) is the name of a currency, a technology, and a movement. A bitcoin (small b) is a unit of this currency.

Example: "After hearing about Bitcoin, I've installed a Bitcoin client and bought 3 bitcoins."

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