In a written language, a logogram, also logograph or lexigraph, is a written character that represents a semantic component of a language, such as a word or morpheme. Chinese characters as used in Chinese as well as other languages are logograms, as are Egyptian hieroglyphs and characters in cuneiform script. A writing system that primarily uses logograms is called a logography. Non-logographic writing systems, such as alphabets and syllabaries, are phonemic: their individual symbols represent sounds directly and lack any inherent meaning. However, all known logographies have some phonetic component, generally based on the rebus principle, and the addition of a phonetic component to pure ideographs is considered to be a key innovation in enabling the writing system to adequately encode human language.