Siemens are a SI unit measurement of electrical conductivity (the ability of something to transmit electricity) of something. It also measures how easily a current passes through something, and how strongly a material blocks electrical energy. The unit is named after Ernst Werner von Siemens. Like other SI units named after people, the symbol is capitalized, but the name of the unit is not. In English, the same word (siemens) is used for both the singular and plural.