base units are the building blocks of the system and all the other units are derived from them. Derived units The derived units in the SI are formed by powers, products, or quotients of the base units and are potentially unlimited in number. Derived units are associated with derived quantities; for example, velocity is a quantity that is derived from the base quantities of time and length, and thus the SI derived unit is metre per second (symbol m/s). The dimensions of derived units can be expressed in terms of the dimensions of the base units. Combinations of base and derived units may be used to express other derived units. For example, the SI unit of force is the newton (N), the SI unit of pressure is the pascal (Pa)—and the pascal can be defined as one newton per square metre (N/m2). {| class="wikitable floatleft" style="margin:1em auto 1em auto;line-height:1.4" |+ SI derived units with special names and symbols |- ! scope="col" | Name ! scope="col" | Symbol ! scope="col" | Quantity ! scope="col" | In SI base units ! scope="col" | In other SI units |- ! scope="row" | radian | style="text-align:center;"| rad | plane angle | style="text-align:center;"| m/m | style="text-align:center;"| 1 |- ! scope="row" | steradian| style="text-align:center;"| sr | solid angle | style="text-align:center;"| m2/m2 | style="text-align:center;"| 1 |- ! scope="row" | hertz | style="text-align:center;"| Hz | frequency | style="text-align:center;"| s−1 | |- ! scope="row" | newton | style="text-align:center;"| N | force, weight | style="text-align:center;"| kg⋅m⋅s−2 | |- ! scope="row" | pascal | style="text-align:center;"| Pa | pressure, stress | style="text-align:center;"| kg⋅m−1⋅s−2 | style="text-align:center;"| N/m2 = J/m3 |- ! scope="row" | joule | style="text-align:center;"| J | energy, work, heat | style="text-align:center;"| kg⋅m2⋅s−2 | style="text-align:center;"| N⋅m = Pa⋅m3 |- ! scope="row" | watt | style="text-align:center;"| W | power, radiant flux | style="text-align:center;"| kg⋅m2⋅s−3 | style="text-align:center;"| J/s |- ! scope="row" | coulomb | style="text-align:center;"| C | electric charge | style="text-align:center;"| s⋅A | |- ! scope="row" | volt | style="text-align:center;"| V | electric potential, voltage, emf | style="text-align:center;"| kg⋅m2⋅s−3⋅A−1 | style="text-align:center;"| W/A = J/C |- ! scope="row" | farad | style="text-align:center;"| F | capacitance | style="text-align:center;"| kg−1⋅m−2⋅s4⋅A2 | style="text-align:center;"| C/V = C2/J |- ! scope="row" | ohm | style="text-align:center;"| Ω | resistance, impedance, reactance | style="text-align:center;"| kg⋅m2⋅s−3⋅A−2 | style="text-align:center;"| V/A = J⋅s/C2 |- ! scope="row" | siemens | style="text-align:center;"| S | electrical conductance | style="text-align:center;"| kg−1⋅m−2⋅s3⋅A2 | style="text-align:center;"| Ω−1 |- ! scope="row" | weber