The International System of Units, the SI system, is a standard system of measurement used around the world.
Length
The SI unit of length is the metre, m. Centimetres, cm, and kilometres km are also commonly used. Length is a measurement of Distance.
Mass
The SI unit of mass is the kilogram, kg. Mass is a measure of how much matter something contains. An electron balance can be used to find mass. Grams, g, are commonly used to measure small amounts of mass.
Time
The SI unit of time is the second, s. Time can be measured using a stopwatch.
Temperature
The SI unit of temperature is the Kelvin. temperature is a measure of how hot something is. There are different scales. Celcius, Fahrenheit and Kelvin. On the Celsius scale, 0C is the temperature at which water freezes over and 100C is the temperature at which water boils.