Aztec writing had three primary functions, namely to mark calendrical dates, to record accounting mathematical calculations, and to write names of people and places. No continuous texts like those of the Maya or Olmec writing system has been be found.
The writing system of the Aztecs is very rudimentary. Its core consists of a set of calendrical signs and a number system. Like other Mesoamerican people, the Aztecs used the 260-day sacred calendar, which in Nahuatl (Aztec) was called tonalpohualli. The tonalpohualli is essentially two parallel and interlocking cycles, one of 20 days (represented by "day signs"), and one of 13 days (represented by numbers called "coefficients"). The following are the 20 day signs in the Aztec sacred calendar. The Nahuatl names are in red, and their meanings in English are in blue.
A date in the tonalpohualli is composed of a day sign and and a coefficient. So, for example, the first day in the 260-day cycle would be 1 Cipactli. As both the day sign and the coefficient moves forward, the next day would be 2 Ehecatl. This goes on until 13 Acatl is reached, at which point the coefficient cycle loops back to 1, and hence the next day would be 1 Ocelotl. Similarly, upon reaching the last day sign on day 7 Xochitl, the day sign cycle goes back to the first sign, and the next day would be 8 Cipactl.
The Aztecs had a 365-day solar calendar called xiuhpohualli, which consisted of 18 months of 20 days, and an unlucky 5-day period at the end of the year. However, they rarely recorded dates in the solar calendar on manuscripts, and never on monuments.
In addition, like other Mesoamerican cultures, the Aztecs also employed the Calendar Round, a 52-year period created by interlocking the 260-day and 365-day cycles. A year in the Calendar Round was named by the tonalpohualli name of last day of the last month in the xiuhpohualli for that year. Because of the way the math worked out, only four day signs, namely Calli, Tochtli, Acatl, and Tecpatl, could be part of a year's name, and hence they were called "year bearers". Accompanying the year bearers were coefficients, which could range from 1 to 13. To distinguish Calendar Round years from days in the 260-day calendar, years glyphs were drawn inside rectangular "cartouches". A good example occurs in the Codex Telleriano-Remensis, a document written after the Spanish Conquest but at a time when knowledge of the pre-Columbian culture was still available. In this document, Aztec years are correlated to Western Gregorian years.
As you have probably gathered by now, Aztec numbers are represented by long sequences of dots. In general, the Aztecs almost exclusively used dots on manuscripts as well as on stone monuments, but the more ancient bar-and-dot system does make rare appearances on carved monuments as well, primarily due to artistic consideration. The dot system, while feasible for calendrical use (since no number will ever exceed 20), was impossible when dealing with accounting, especially since the Aztecs had to record large amounts of tribute frequently demanded from its provinces. The Codex Mendoza, another post-Conquest manuscript, depicted life in Central Mexico around the time of conquest and also contained a section on the tribute exacted by the Aztec Empire. To count items in excess of 20 efficiently, the Aztecs used glyphs for the numbers 20 (a flag), 400 (a feather), and 8000 (a bag of incense).
For example, the number 500 would be a feather and five flags (400 + 5 x 20 = 500). To indicate that the multiple glyphs forming a number belong to a single sign group, a line is drawn to connect all the glyphs. The line is then connected to the object it is counting.
In addition to calendrical and numeric signs, a number of highly pictorial logograms were used to write down personal names, names of places, and historical events. For example, there are many records of the Aztec army conquering other cities documented in the Codex Mendoza. To show that a city has been conquered, the city's name is written next to the "conquered" glyph which is a temple (pyramid) in smoke and flames with its top toppling over. In the following example, the ancient cities Colhuacan and Tenayucan were shown to be conquered. And to drive the point home, Aztec warriors are shown with captives.
Since Aztec names tend to be composed of words in the Nahuatl language, names are often written as groups of highly pictorial logograms that make up the roots of the name. However, sometimes names also contain phonetic elements in the form of rebus writing to either disambiguate the reading, or explicitly spell out the entire name.
The following is a small set of toponyms (place names) as found in various post-Conquest manuscripts. The first set of examples are names spelled out mostly by pictorial logograms.
Explanations for the previous example:
- Chilapan, from chilli + apan, meaning "at the water of chiles". The picture of a chile pepper provides the first root chilli, while the ending apan, meaning "place of water", is provided by water in a canal.
- Colhuacan, from colhua + can, meaning "twisted or crooked hill". Clearly illustrated by the twisted hill top.
- Ocelotepec, from ocelotl + tepec, meaning "hill of the ocelot". The ocelot is wildcat common to the Americas and is depicted here by its head. Also, in Nahuatl, can is synonymous with tepec, and hence both words are represented by the same sign.
- Coatlan, from coatl + tlan, meaning "place abundant with snakes". Here we encounter the first example of using phonetic elements. Teeth in Nahuatl is tlantli, and so a set of teeth is conventionally read as tlan, which is a Nahuatl suffix meaning "place abundant with".
- Coatzinco, from coatl + tzin + co, meaning "little Coatlan". The ending tzinco is represented phonetically by the lower half of a crouching man, which in reality carries the meaning of 'buttocks'. The word 'buttocks' in Nahuatl is tzintli, and conveniently spells out the syllable tzin.
- Ahuacatlan, from ahuacatl + tlan, meaning "place abundant with avocadoes". Once again the ending tlan is represented by a set of teeth, but this time incorporated into the avocado tree.
Explanations for the previous example:
- Capulteopan, from capulli + teopan, meaning "the temple of the neighborhood". The word "temple", teopan, is clearly depicted, but "neighborhood", capulli is harder to visualize. Rebus writing comes to the rescue in that capulli is phonetically similar to capulin, which is a Mexican plant related to cherries. By drawing the capulin tree, the sound capul is expressed.
- Mapachtepec, from mapach + tepec, meaning "near the hill of the raccoon". Instead of drawing a raccoon, mapach in Nahuatl, a hand (maitl) and a piece of moss (pachtli) are drawn together. By taking the first syllables of both words, /ma/ and /pach/, we obtain mapach.
- Miacatla, from mitl + aca + tla(n), meaning "place abundant with arrows". The picture of an arrow, mitl logographically represents the first part of the word. The ending, acatla, is provided phonetically by the depiction of a reed, acatl in Nahuatl.
- Amacoztitlan, from amatl + cozti + tlan, meaning "place abundant with yellow papers". The concept of a yellow paper is expressed in the yellow rectangular in the middle of the signs. Water, atl, on the bottom is used phonetically to provide the initial vowel /a/, reinforcing the reading of "amacoztli". The set of teeth on the top phonetically provide the ending tlan.
- Pantepec, from pan + tepec, meaning "upon the hill". The particle pan carries the meaning of "above" or "upon", which is depicted by the picture of a flag, pantli in Nahuatl.
- Tepechpan, from tepexitl + pan, meaning "above the crag". The phonetic elements consist of tetl and petlatl, which together approximates the initial tepech. The final syllable pan is indicated figuratively by placing a house above the tepech component at the bottom, effectively giving the reading of "above the crag".
Signs used for phonetic values are not randomly drawn from the logograms but actually from a very predictable and minimal set. But, most of all, since the knowledge of the underlying language, Nahuatl, is essential to fully interpret the glyphs, the Aztec script most certainly classifies as a writing system.
Despite the limitation of their writing systems, the Central Mexicans must have produced countless numbers of manuscripts with subject matters as diverse as time-keeping, astronomy and astrology, mythology, genealogy, and history, all attesting to the power of the written word.
The toponyms in the previous examples were taken from Nombres Geográficos de México project website.