ABSTRACT
Measurement is the act of determining the extent of something in relation to a standard. Standardization of measurement, while important in everyday affairs of course, is absolutely critical in science. Units are the dimensions or quantities on which measurements are based. For many of the phenomena we wish to measure, e.g. distance and weight, different units are in use, which can cause some confusion unless conversion values are known. In the interests of standardization the international scientific community has agreed a set of units, known as SI units from the French Système International d’Unités. For each unit there is an agreed symbol. Sometimes the symbol is a capital letter, or it begins with one. This indicates the symbol is named after someone. The other symbols consist of one or two lower case letters. The SI units for a range of common phenomena are introduced in this section together with some elaboration about what it is they measure. Some of the other units you may encounter, and the values used to convert them to the appropriate SI units, are also shown.
