Système International d’Unités, an internationally agreed group of units of measurement, used especially in scientific work. The system comprises seven basic and two supplementary units. The basic units are the: metre (m); kilogram (kg); second (s); ampere (A); kelvin (K); mole (mol); and candela (cd). The supplementary units are the: radian (rad); and steradian (sr). A further 18 units are derived from these: becquerel (Bq); coulomb (C); farad (F); gray (Gy); henry (H); hertz (Hz); joule (J); lumen (lm); lux (lx); newton (N); ohm (Ω‎); pascal (Pa); siemens (S); sievert (Sv); tesla (T); volt (V); watt (W); and weber (Wb). See si units, conversions, and multiples (appendix d).