System of human visual communication using signs or symbols associated by convention with units of languagemeanings or soundsand recorded on materials such as paper, stone, or clay. Its precursor was pictography. Logography, in which symbols stand for individual words, typically develops from pictography. Logography requires thousands of symbols for all possible words and names. In phonographic systems, the symbol associated with a word also stands for similar- or identical-sounding words. Phonographic systems may evolve to the point where symbols represent syllables, constituting a syllabary. An alphabet provides symbols for all the consonants and vowels.