In a written language, a logogram (from Ancient Greek logos 'word', and gramma 'that which is drawn or written'), 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.

Some of the earliest recorded writing systems are logographic; the first historical civilizations of Mesopotamia, Egypt, China and Mesoamerica all used some form of logographic writing.

All logographic scripts ever used for natural languages rely on the rebus principle to extend a relatively limited set of logograms: A subset of characters is used for their phonetic values, either consonantal or syllabic. The term logosyllabary is used to emphasize the partially phonetic nature of these scripts when the phonetic domain is the syllable. In Ancient Egyptian hieroglyphs, Ch'olti', and in Chinese, there has been the additional development of determinatives, which are combined with logograms to narrow down their possible meaning. In Chinese, they are fused with logographic elements used phonetically; such "radical and phonetic" characters make up the bulk of the script. Ancient Egyptian and Chinese relegated the active use of rebus to the spelling of foreign and dialectical words.

Logoconsonantal scripts have graphemes that may be extended phonetically according to the consonants of the words they represent, ignoring the vowels. For example, Egyptian

was used to write both sȝ 'duck' and sȝ 'son', though it is likely that these words were not pronounced the same except for their consonants. The primary examples of logoconsonantal scripts are Egyptian hieroglyphs, hieratic, and demotic: Ancient Egyptian.

Logosyllabic (or morphosyllabic) scripts have graphemes which represent morphemes, often polysyllabic morphemes, but when extended phonetically represent single syllables. They include cuneiform, Anatolian hieroglyphs, Cretan hieroglyphs, Linear A and Linear B, Chinese characters, Maya script, Aztec script, Mixtec script, and the first five phases of the Bamum script.

A peculiar system of logograms developed within the Pahlavi scripts (developed from the abjad of Aramaic) used to write Middle Persian during much of the Sassanid period; the logograms were composed of letters that spelled out the word in Aramaic but were pronounced as in Persian (for instance, the combination m-l-k would be pronounced "shah"). These logograms, called hozwārishn (a form of heterograms), were dispensed with altogether after the Arab conquest of Persia and the adoption of a variant of the Arabic alphabet.^{[citation needed]}

All historical logographic systems include a phonetic dimension, as it is impractical to have a separate basic character for every word or morpheme in a language. In some cases, such as cuneiform as it was used for Akkadian, the vast majority of glyphs are used for their sound values rather than logographically. Many logographic systems also have a semantic/ideographic component (see ideogram), called "determinatives" in the case of Egyptian and "radicals" in the case of Chinese.