This paper discusses the system of units of measurement, the histroical development of units of measurement, meterology and measurement errors. The following discusses what a units od measurement actually means, how it is interpreted, and how it came about. In addition to various systems of units of measurement, the paperrefers to the units of measurement of the SI constitution. There is talk of problems in measurement, errors. The international system of units is the most widespread in the whole world. Until the development and emergence of the metric system, when the first international measurement standards inn the form of material diameters of meters andkilograms were presentedm there were a large number of different units of measurement used to measure the same size, making trade, traffic, taxation and other human activities was necessary, the development of science and activitiy people needed more and more units of measurement, which required some standard to facilitate human communication. After some time, standards were set because accuracy in measurement is also required. There are different standards as well as different units of measurement in the world. The paper describes the basic units of measurement, which is actually a measurement, what kind of measuring devices we have.