Cuneiform is a writing system in which signs are carved on soft clay tablets using a reed stylus. Cuneiform writing was used throughout the ancient world for more than three millennia until around 75 c.e. Continuous lines etched into the clay formed the earliest signs. Because drawing was a relatively slow process, signs were later created with individual cuneus, or wedge-shaped strokes, impressed into the clay.

The wedge shapes became so characteristic of the script that, even though unnecessary, they were included when inscriptions were later engraved in stone or metal. The earliest cuneiform texts were excavated at the southern Mesopotamian city of Uruk and dated just before 3000 b.c.e. Denise Schmandt-Besserat proposed a sequence in which small clay tokens found throughout the Near East are the precursors to cuneiform writing.

From the eighth millennium b.c.e., clay tokens of various shapes were used to represent quantities of items in order to keep track of agricultural products. To prevent unauthorized tampering, tokens were sealed and enclosed in hollow clay envelopes.

Because the tokens would be hidden, they were first impressed onto their envelopes for easy identification. Soon it was recognized that the impressions themselves could convey the same information, without the cumbersome use of tokens. It is plausible that the etched sign was a natural progression from the impressed image.

Most of the early cuneiform signs originated as pictograms, which attempt to replicate the appearance of objects they represent. For example, the sign for a bull resembles a bull’s head. Sometimes these pictograms were used symbolically to express the natural association of ideas.

The sign picturing a star was also used to denote heaven or god, since the celestial realm was considered an abode of the gods. At the earliest stage numbers were not depicted in the abstract (for example, five) but were inextricably linked to the item being counted (for example, five grain rations).

This way of conceptualizing numbers derived from the token system, in which each token simultaneously indicated quantity and identity of the object represented. Later development, however, led to abstract, context-independent numerical signs.

A basic cuneiform sign could be qualified by etching hatched lines over the part to be accentuated, a procedure known as gunification. In this manner, by etching the appropriate place on the sign for head, a new sign for mouth could be signified. Furthermore, combining two or more existing signs may create new signs.

The sign for woman closely juxtaposed with the sign for foreign land yielded the sign for slave woman. Thus, the sign for bread within the sign for mouth resulted in a new sign meaning to eat. Logographic writing of the signs can obscure the language used in a cuneiform text. This means that each sign represents a word and, thus, gives no indication of how that word is to be pronounced.

For example, the sign for king could be read in Sumerian as lugal or in Akkadian as sharrum. Indeed, the earliest use of cuneiform was merely mnemonic and not as a visual means to represent spoken language. In some archaic texts the signs even seem to be written in a random order, showing no attempt to reflect the linear sequence of spoken language.

Nonetheless, the language of the Uruk tablets is shown to be Sumerian because of rebus writing, whereby a sign is used to represent different words or grammatical forms with the same pronunciation. For example, the sign for arrow (pronounced as “ti”) also has the meaning life. This would make sense only in Sumerian, where the word life is pronounced as “ti.”

The total number of cuneiform signs is limited by polyphony, the case that a single sign may be read in different ways. Thus, the sign picturing a human foot could be read in Sumerian as gin (to walk), gub (to stand), or tum (to bring). Such ambiguity in meaning is sometimes clarified by the use of a determinative sign, which indicates the semantic category that the word belongs to.

For example, the same sign could mean “day,” “Sun,” or even “sun god.” By attaching the god determinative before this sign, the meaning becomes unequivocal. Conversely, cuneiform has cases of homophony, whereby different signs share the same pronunciation.

The use of logograms (word signs) for verbs suited the Sumerian language, which varied by adding affixes to an unchanged verbal root. By contrast, Akkadian inflected its verbs in such a way that could not be expressed by using the same cuneiform sign. Accordingly, with the spread of Akkadian in Mesopotamia, there was pressure to apply the rebus principle to cuneiform signs so that they indicated syllables instead of whole words.

For example, the Akkadian verb “he gave” (pronounced as “iddin”) could be expressed by a sequence of these three syllable signs: id + di + in. This procedure preserved in writing the vowels of Akkadian, in contrast to the use of purely consonantal alphabetic scripts for several other Semitic languages. In the third millennium b.c.e. cuneiform was also used for the Semitic language at Ebla in northern Syria, as well as the Elamite language in western Iran.

With Akkadian’s ascendancy as the lingua franca, the use of cuneiform spread as far as Egypt. Hittite, Hurrian, and Urartian documents have all been found in cuneiform script. When early pictograms are oriented to a position natural to the objects they depict, the signs appear in columns from top to bottom, and the columns are read from right to left.

However, at some point in time, cuneiform signs experienced a 90-degree rotation in the counterclockwise direction (i.e., signs were now read in each row from left to right, and the rows read from top to bottom). The flexibility, with which tablets would be rotated during cuneiform writing, may have helped ancient scribes become familiar with reading signs in different orientations.