### What is a 'Satoshi'?

• I am aware that Satoshi Nakamoto is the author of the paper that originated Bitcoin and the creator of the original bitcoin client. However, I often hear the term Satoshi as if it was a monetary unit.

What is a Satoshi?

• A Satoshi is the smallest fraction of a Bitcoin that can currently be sent: 0.00000001 BTC, that is, a hundredth of a millionth BTC. In the future, however, the protocol may be updated to allow further subdivisions, should they be needed.

Further examples of units

• 1 BTC = 1,000 mBTC (millibitcoin)
• 1 BTC = 1,000,000 μBTC (microbitcoin)
• 1 BTC = 100,000,000 Satoshis
• 1 mBTC = 100,000 Satoshis
• 1 μBTC (microbitcoin) = 100 Satoshis

Note that it's possible that future protocol versions will introduce amounts smaller than a Satoshi, if deemed required by the community. I'm not sure how likely this is. http://bitcoin.stackexchange.com/questions/122/will-we-ever-need-smaller-amounts-of-bitcoin-than-a-satoshi

@eMansipater It might be worth editing your answer just a touch to ensure that people don't think that there is a limit to the number of decimal places possible.

It's Michael's answer, but I updated it anyway.

Isn't one BTC a HUNDRED million Satoshis?

yes 1 btc is divided into 100 million satoshi

1 uBTC = 0.000001 BTC = 1 bit

@ripper234 not likely, when 1BTC = US\$1,000,000 then 1 Satoshi will be exactly 1c.

@ripper234, I think the protocol would only update once 1 Satoshi is worth more than 1 cent or smallest denomination in one of today's fiat currencies since it would be needed by that culture that used BTC.

While not in raw Bitcoin, we are seeing milli satoshis now in Lightning Network