The ampere (/ ˈ æ m p ɪər, æ m ˈ p ɪər /; symbol: A), often shortened to "amp", is the base unit of electric current in the International System of Units (SI). It is named after André-Marie Ampère (1775–1836), French mathematician and physicist, considered the father of electrodynamics.. The International System of Units defines the ampere in terms of other base units by measuring ...