The scientist’s starter kit কী?

The world has agreed on common units, one family per quantity:

1. length: the metre ($\mathrm{m}$), with its offspring the kilometre ($1\,\mathrm{km} = 1000\,\mathrm{m}$), centimetre ($100\,\mathrm{cm} = 1\,\mathrm{m}$) and millimetre ($1000\,\mathrm{mm} = 1\,\mathrm{m}$);
2. mass: the kilogram ($\mathrm{kg}$), with the gram ($1\,\mathrm{kg} = 1000\,\mathrm{g}$) and milligram ($1000\,\mathrm{mg} = 1\,\mathrm{g}$);
3. time: the second ($\mathrm{s}$), with the minute ($1\,\mathrm{min} = 60\,\mathrm{s}$) and hour ($1\,\mathrm{h} = 60\,\mathrm{min} = 3600\,\mathrm{s}$);
4. temperature: the degree Celsius (${}^{\circ}\mathrm{C}$);
5. volume of liquids: the litre ($\mathrm{L}$), which we measure out in the next chapter.