Logograms are symbols used in writing language that stand for an entire word or morpheme, a meaningful unit of speech. Examples of logograms in English are numerals and symbols such as # (pound or number) and % (percent). Many of the world's earliest writing systems, such as the Ancient Egyptian hieroglyphs, used logograms. Logograms have a history of use around the world, from Asia and the Middle East to Africa and the Americas. While many modern writing systems use logograms to some degree, there are no purely logogrammatical writing systems in use today.
Logograms are characterized by being unrelated to the pronunciation of the word they represent; they cannot be sounded out, as words written with an alphabet may be. For this reason, the same logograms may be used throughout many languages, as is the case with the numerals used in English. Logograms are sometimes pictograms, visually related to the word or morpheme they represent, and sometimes ideograms, representing more abstract ideas.
As logogrammatical writing systems evolve, the logograms often become so reduced or stylized that their meaning is no longer immediately obvious from their appearance. This is the case in writing systems like Cuneiform and Chinese. Even the Roman letters used for English and most other European languages are derived from ancient pictograms representing example words that started with each letter.
Logogrammatical writing systems also increasingly make use of phonetic elements as they evolve to handle new language situations. For example, many logogrammatical systems of the ancient world, such as Mayan and Aztec glyphs, used phonetic symbols to supplement logograms when logograms themselves were not sufficient for expression. In fact, a writing system must have a phonetic component in order to be complete; full expression is simply not possible otherwise. This latter situation was the case with the ancient Nahuatl writing system, which served as more of an outline of a text than a record of specific words; different people reading the same ancient Aztec text aloud could theoretically use very different words. Full logogrammatical writing systems may use logograms to represent phonemes (sounds), as in the writing system that evolved into the Roman alphabet, or they may combine phonetic symbols with semantic ones, as in Chinese and the Egyptian hieroglyphs.