The unit symbols defined by the Bureau International des Poids et Mesures under the Metre Convention. Grouped because they are the rare case where a symbol's meaning is genuinely official — the SI Brochure states each name and symbol exactly, including the capitalisation rules that make mm and Mm differ by a factor of a billion. The group also makes the boundary visible: the degree Fahrenheit, the angstrom and the decibel's reference levels sit alongside them in ordinary use and are not SI at all, and each of those records says so in its first line.
A lower-case m, the SI unit symbol for the metre.
The two-letter symbol kg, the SI unit symbol for the kilogram.
A lower-case s, the SI unit symbol for the second.
A capital A, the SI unit symbol for the ampere.
A capital K, the SI unit symbol for the kelvin.
The three letters mol, the SI unit symbol for the mole.
The two letters cd, the SI unit symbol for the candela.
The two letters Hz, the SI unit symbol for the hertz.
A capital N, the SI unit symbol for the newton.
The two letters Pa, the SI unit symbol for the pascal.
A capital J, the SI unit symbol for the joule.
A capital W, the SI unit symbol for the watt.
A capital V, the SI unit symbol for the volt.
A capital F, the SI unit symbol for the farad.
A capital T, the SI unit symbol for the tesla.
The two letters lm, the SI unit symbol for the lumen.
The two letters lx, the SI unit symbol for the lux.
The two letters Bq, the SI unit symbol for the becquerel.
The two letters Sv, the SI unit symbol for the sievert.
A degree sign followed by a capital C, marking a temperature in Celsius.
A lower-case Greek mu with a straight descender, used as the SI prefix for one millionth.
A lower-case k, the SI prefix for a factor of one thousand.
A capital or lower-case L, the symbol for the litre.
A degree sign followed by a capital F, marking a temperature in Fahrenheit.
A capital A with a small ring above it, marking a length of 10⁻¹⁰ metres.
The two letters dB, marking a ratio on a logarithmic scale.