Bacteria are mostly unicellular prokaryotic organisms. Bacteria are cells which have their metabolism and reproduce by means of cell division. Bacteria have a number of shapes, including spheres which are called cocci (staphylococcus, streptococcus, pneumococcus, meningococcus, etc.) and rods (colon bacillus, Bordetella pertussis, dysentery bacillus, etc.).
There are two different unit systems: conventional units and SI units.
The International System of Units, or SI Units (abbreviated SI from French: Le Système international d'unités) is the modern form of the metric system and is the world's most widely used system of measurement, used in both everyday commerce and science.