tlatoani.

Headword: 
tlatoani.
Principal English Translation: 

ruler ("one who speaks"), dignitary, judge, speaker, great lord, king; also used in reference to various high Spanish officials.
James Lockhart, Nahuatl as Written: Lessons in Older Written Nahuatl, with Copious Examples and Texts (Stanford: Stanford University Press and UCLA Latin American Studies, 2001), 238.

Orthographic Variants: 
tlahtoani, tlatuani, tlahtuani, tlahtohuani, tlatohuani
IPAspelling: 
tɬɑhtoɑːni
Alonso de Molina: 

tlatoani. hablador, o gran señor.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 140v. col. 1. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

TLAHTOĀNI ruler, governor, one who issues proclamations and commands / hablador o gran señor (M), el rey (C), el gobernador (C), autoridad (del pueblo), jefe, presidente (T) Except in R and Z, which have them both in free singular form, TLAHTOĀNI and TLAHTOHQUI are suppletive, with the former as a free singular and the latter in inflected and compounded forms. See TLAHTOĀ.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 266.

Lockhart’s Nahuatl as Written: 

tlahtoani = ruler, dignitary, judge, speaker, great lord, king; also used in reference to various high Spanish officials

pl. may refer to a group of notables who are not rulers. the abs. pl. and all other forms are based on the pret. agentive tlahtoh, no longer used in the abs. sing. tla-, ihtoa, -ni
James Lockhart, Nahuatl as Written: Lessons in Older Written Nahuatl, with Copious Examples and Texts (Stanford: Stanford University Press and UCLA Latin American Studies, 2001), 238.

Attestations from sources in English: 

"...literally 'speaker' and in practice the dynastic ruler of an altepetl."
Annals of His Time: Don Domingo de San Antón Muñón Chimalpahin Quauhtlehuanitzin, James Lockhart, Susan Schroeder, and Doris Namala, eds. and transl. (Stanford: Stanford University Press, 2006), 21.

in tlatoani ceoallo hecauhio, malacaio, puchotl, aueuetl, tequaio, imacaxio, tleio, tocaiô. = The ruler [is] a shelter-- fierce, revered, famous, esteemed; well reputed, renowned. (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 10 -- The People, No. 14, Part 11, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1961), 15.

Teutl Tlahtohuani Dios = God, the highest ruler Susanne Klaus, Uprooted Christianity: The Preaching of the Christian Doctrine in Mexico, Based on Franciscan Sermons of the 16th Century Written in Nahuatl (Bonn: Bonner Amerikanistische Studien e. V. c/o Seminar für Völkerkunde, Universität Bonn, 1999), 249.

with vowel length indicated (and h for the glottal stop):
tlahtohuāni, tlahtoāni

tlatoque = abs. pl. of tlahtoāni, based on the pret. agentive
James Lockhart, Nahuatl as Written: Lessons in Older Written Nahuatl, with Copious Examples and Texts (Stanford: Stanford University Press and UCLA Latin American Studies, 2001), 239.

(pl. tlatoque) usually dynastic ruler of a sovereign polity; in this book translated as ruler
The Tlaxcalan Actas: A Compendium of the Records of the Cabildo of Tlaxcala (1545–1627), eds. James Lockhart, Frances Berdan, and Arthur J.O. Anderson (Salt Lake City: University of Utah Press, 1986), 154.

tlahtoca- = combining form of tlahtoani; based on the pret. agentive of ihtoa
James Lockhart, Nahuatl as Written: Lessons in Older Written Nahuatl, with Copious Examples and Texts (Stanford: Stanford University Press and UCLA Latin American Studies, 2001), 238.

tohueytlahtocauh = our great ruler
The Tlaxcalan Actas: A Compendium of the Records of the Cabildo of Tlaxcala (1545–1627), eds. James Lockhart, Frances Berdan, and Arthur J.O. Anderson (Salt Lake City: University of Utah Press, 1986), 20.

huey tlatoani Dios = the great ruler God (Santa Ana, Toluca Valley, 1728)
Caterina Pizzigoni, ed., Testaments of Toluca (Stanford: Stanford University Press and UCLA Latin American Center Publications, 2007), 117.

dynastic ruler
S. L. Cline, Colonial Culhuacan, 1580–1600: A Social History of an Aztec Town (Albuquerque: University of New Mexico Press, 1986), 237.

tohueytlahtocatzin = our great ruler
Byron McAfee, translation of the Techialoyan manuscript from Santa Mara Zolotepec or Ocelotepec; University of California, Los Angeles, Special Collections

tlacatlatoani = ruler of the people(?), something like tlacatecuhtli(?)
See the Techialoyan manuscript from San Martín Ocoyacac located in the Staatsbibliothek Preussischer Kulturbesitz, Ms America No. 7.

ytlatocayo = the rulership of
[Ocoyacac Techialoyan, 2vta.]

tlatoani = speaker; supreme ruler
Susan Kellogg, Law and the Transformation of Aztec Culture, 1500–1700 (Norman and London: University of Oklahoma Press, 1995), 227.

Auh intla çiuapilli vnan tlacatia iuhquin tlatoani mochiva = And if a noblewoman was born thern, she became like a ruler.
Fray Bernardino de Sahagún, Primeros Memoriales, ed. Thelma D. Sullivan, et al. (Norman: University of Oklahoma Press, 1997), 161.

tlatuane = addressing a tlatoani

In a testament from 1634, San Cristóbal Ecatepec, pertaining to don Hilario de Gante, one finds an impressive array of tlatoque witnesses, including men from Tizayuca, Tehuacan, Jaltocan, Jilotzinco, Acolma, Huaquilpan, and Zumpango.
Vidas y bienes olvidados: Testamentos en náhuatl y castellano del siglo XVII, vol. 3, Teresa Rojas Rabiela, et al, eds. (México: CIESAS, 2002), 204–207.

tlahtocatilmahtli = the cape of high nobility, the lord's cape
Justyna Olko, Turquoise Diadems and Staffs of Office: Elite Costume and Insignia of Power in Aztec and Early Colonial Mexico (Warsaw: Polish Society for Latin American Studies and Centre for Studies on the Classical Tradition, University of Warsaw, 2005), 202.

Attestations from sources in Spanish: 

notlaçotatzin tlatohuani don Martin Ceron = mi querido padre, al señor don Martín Serón (Xochimilco, 1650)
Vidas y bienes olvidados: Testamentos en náhuatl y castellano del siglo XVII, vol. 3, Teresa Rojas Rabiela, et al, eds. (México: CIESAS, 2002), 244–245.

tlatuhani quezcopixqui = cavayero casiqui (eighteenth-century translation, Guerrero)
Danièle Dehouve, "Dos relatos sobre migraciones nahuas en el Estado de Guerrero," Estudios de Cultura Náhuatl 12 (1976), 139, 142.