Bitcoin Standard Units
Bitcoin, or BTC is the standard term for one hundred million Satoshis, and is the most common unit reference. Referring to coin values should be done in lower case, for example ten bitcoins.
This is the standard unit used in the Bitcoin Core reference client.
Microbitcoin, or bit or μBTC is a term for a one hundred Satoshis, meaning one million bits equal one bitcoin. The justification for this term is to avoid the use of fractional units for ease of use reasons.
A millibit, or mBTC is a term for a hundred thousand Satoshis, so one thousand millibits equals one Bitcoin. The name originates from a BitcoinTalk web poll conducted in May of 2011. The term also extends to millie, and millibitcoin
Support for this unit is the second most widespread, after BTC, and it is included as an option in the Bitcoin Core reference client.
A Satoshi, or sat. is the smallest representable unit of Bitcoin that can be expressed in a Blockchain transaction. The name was bestowed in honor of Satoshi Nakamoto, the creator of Bitcoin, he did not reference or create the unit himself. The idea is credited to a forum poster in February of 2011 discussing potential names for smaller units.
A single bitcoin unit represents one hundred million fractional Satoshi units. The unit of measurement is generally considered impractically small, so support for it within user interfaces is extremely limited.
Drawing inspiration from the Japanese name of Satoshi Nakamoto, Japanese characters have been suggested as representing a Satoshi: ㋛, サ, シ, し