Historically Nahuatl has been written with greatly differing orthographies because no institution has governed its spelling. This is still true for the Classical Nahuatl dialect which is a dead language documented in many historical sources and literature, but spelling of the modern dialects of Nahuatl is governed by the Mexican Secretaría de Educación Publica (federal education ministry), although they do have some difficulties in implementing their orthographic standards in the Nahuatl communities. This article describes and compares some of the different transcription systems of the Nahuatl phonological system that have been used. Classical Nahuatl's phonology Vowels Consonants Orthographical history At the time of the Spanish conquest, Aztec writing used mostly pictographs supplemented by a few ideograms. When needed, it also used syllabic equivalences; Father Diego Durán recorded how the tlàcuilòquê (codex painters) could render a prayer in Latin using this system, but it was difficult to use. This writing system was adequate for keeping such records as genealogies, astronomical information, and tribute lists, but could not represent a full vocabulary of spoken language in the way that the writing systems of the old world or of the Maya civilization could. Aztec writing was not meant to be read, but to be told; the elaborate codices were essentially pictographic aids for teaching, and long texts were memorized. The Spanish introduced the Latin alphabet, which was then utilized to record a large body of Aztec prose and poetry, a fact which somewhat mitigated the devastating loss of the thousands of Aztec manuscripts which were burned by the Spanish (see Aztec codices). Important lexical works (e.g. Alonso de Molina's classic Vocabulario of 1571) and grammatical descriptions (of which Horacio Carochi's 1645 Arte is generally acknowledged as the best) were produced using variations of this orthography. Classical Nahuatl orthography was not perfect, and in fact there were many variations in how it was applied, due in part to dialectal differences and in part to differing traditions and preferences that developed. (The writing of Spanish itself was far from totally standardized at the time.) Today, although almost all written Nahuatl uses some form of Latin-based orthography, there continue to be strong dialectal differences, and considerable debate and differing practices regarding how to write sounds even when they are the same. Major issues include: Whether to follow Spanish in writing sometimes as and sometimes as , or to just use How to write What to do