ca.

Headword: 
ca.
Principal English Translation: 

is (present tense of to be somewhere)

Orthographic Variants: 
cah
IPAspelling: 
kɑh
Alonso de Molina: 

Ca. ni. estar, o ser. preterito. onicatca.
Alonso de Molina, Vocabulario en lengua mexicana y castellana, 1571, (www.idiez.org.mx), f. 10r.

Oncate. son, ay, o estan. dizese de personas que estan en sus casas, o en sus pueblos. i. que no estan ausentes
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, f. 10r., 77r.

Frances Karttunen: 

to be / estar, o ser (M); CĀ preterit-as- present verb; pret: CAH~CATQUI, pret pl: CATEH Since the preterit of this verb is used for the present tense, past tense is expressed with the pluperfect form CATCA. It is suppletive with the verb YE, which is used for the future, the imperative, and the optative. The nonactive YELOHUA is built on the YE verb. The sense of CĀ in context is generally locative or existential. In equational sentences CĀ and YE are used only as vehicles for overt tense marking other than simple present or unspecified time; otherwise they are omitted from the sentence.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 18.

Horacio Carochi / English: 

câ = stative verb to be
niez = I will be (also seen as niyez)
mā nie = may I be
mā xie = may you (informal) be
mā ye = may he/she be
mā tiecan = may we be
mā yecan = may they be
mā nieni = would that I were or had been
mā xieni = would that you (inf.) were or had been
mā yeni = would that he/she were or had been
mā yenî = would that they were or had been
Horacio Carochi, S.J., Grammar of the Mexican language with an explanation of its adverbs (1645), translated and edited with commentary by James Lockhart, UCLA Latin American Studies Volume 89 (Stanford: Stanford University Press, UCLA Latin American Center Publications, 2001), 82–85, 151, 498.

Andrés de Olmos: 

"Esta particula denota algunas vezes afirmacion en platica, o es modo o ornato que tienen en el dezir; otras vezes es verbo sum, es, fui, y diferenciar se ha con la h que se escriue, como parece en la conjugacion; otras vezes es preposicion, otras vezes aduerbio local. Ex.: ca yauh yn Pedro, vel campa yauh yn Pedro adonde va Pedro."
Andrés de Olmos, Arte para aprender la lengua Mexicana, ed. Rémi Siméon, facsimile edition ed. Miguel León-Portilla (Guadalajara: Edmundo Aviña Levy, 1972), 181.

Attestations from sources in English: 

amo yntlal ipan catte = they are on land not theirs (Tlaxcala, 1547)
Beyond the Codices, eds. Arthur J.O. Anderson, Frances Berdan, and James Lockhart (Los Angeles: UCLA Latin American Center, 1976), Doc. 22, 120–121.

tolalpa ocatca = They were in Tollalpan (Cuernavaca region, ca. 1540s)
The Book of Tributes: Early Sixteenth-Century Nahuatl Censuses from Morelos, ed. and transl. S. L. Cline, (Los Angeles: UCLA Latin American Center Publications, 1993), 248–249.

y chicuazemi acticate = There are six included [in the household] (Cuernavaca region, ca. 1540s)
The Book of Tributes: Early Sixteenth-Century Nahuatl Censuses from Morelos, ed. and transl. S. L. Cline, (Los Angeles: UCLA Latin American Center Publications, 1993), 116–117.

More akin to the Spanish form, estar, than the Spanish form, ser:
onca = is, exists
cateh = are, exist
oncate, oncateh = they are, an existential form of ca, comprised of on (directional) & cateh (are)
catca, ocatca, oncatca = were, existed
oncatqui = presently exists, there are
niyez, niez = I will be (someplace)
ca ye = for, since, because
Robert Haskett and Stephanie Wood's notes from Nahuatl sessions with James Lockhart and subsequent research.

Nicān nicâ. = I'm here.
Mēxico ticatê. = We're in Mexico.
Tlaxcallān catê in cihuâ. = The women are in Tlaxcala.
Michel Launey, An Introduction to Classical Nahuatl, translated and adapted by Christopher MacKay (Cambridge: Cambridge University Press, 2011), 43.

Attestations from sources in Spanish: 

tza cetetl yn icac yn calli yhua yn ixquich yn oca tepeuhtonc yn ixquich ytetl mochi = no hay más de una casa y todos aquellos montones de piedras que hay (San Juan Teotihuacan, 1563)
Vidas y bienes olvidados: Testamentos indígenas novohispanos, vol. 2, Testamentos en náhuatl y castellano del siglo XVI, eds., Teresa Rojas Rabiela, Elsa Leticia Rea López, Constantino Medina Lima (Mexico: Consejo Nacional de Ciencias Tecnología, 1999), 138–139.

tza yeyo ycaltzintli amo yhua ymili = solas las casa y no las tierras (San Juan Teotihuacan, 1563)
Vidas y bienes olvidados: Testamentos indígenas novohispanos, vol. 2, Testamentos en náhuatl y castellano del siglo XVI, eds., Teresa Rojas Rabiela, Elsa Leticia Rea López, Constantino Medina Lima (Mexico: Consejo Nacional de Ciencias Tecnología, 1999), 138–139.

quentica (quen tica) = como estas
Pedro de Arenas, Vocabulario Manual de las Lenguas Castellana, y Mexicana (Mexico: Henrico Martínez, 1611), 1.

yn mochinti justisia taltepetli xa yexhantzitzi quimotlalilisque ynfirma ykan tlaneltilis nicgualtia notestamento = la justicia de nuestro pueblo, que sus mercedes han de firmar para que sea cierto que empiezo mi testamento (Tecamachalco, Puebla, "1548", transl. 1717)
Vidas y bienes olvidados: Testamentos indígenas novohispanos, vol. 2, Testamentos en náhuatl y castellano del siglo XVI, eds., Teresa Rojas Rabiela, Elsa Leticia Rea López, Constantino Medina Lima (Mexico: Consejo Nacional de Ciencias Tecnología, 1999), 82–83.

nica o nicatqui = yo estoy;
nicatca = yo estaba, estuve, y habia estado;
niez = yo seré o estaré (Tetzcoco, 1595)
Antonio del Rincón, Arte mexicana, 32, reproducida digitalmente por el Internet Archive, http://archive.org/stream/artemexicana00rincrich/artemexicana00rincrich_....