When units are named after an individual their symbol should begin with a capital letter (for example: ampere, A; kelvin, K; hertz, Hz; or coulomb, C). In all other cases, except the litre, they begin with a lower case letter (for example: metre, m; second, s; or mole, mol). The symbol for the litre is an exception; either a lower case letter ‘l’ or a capital ‘L’ may be used, the capital is allowed in this case to avoid confusion between the lower case letter l and the number one, 1.
