Principal English Translation:
may, let, if, used with the optative of verbs instead of mā for maximum politeness; and xi- (imperative) = "please"; a polite way of phrasing the imperative
something; conjunction
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), 235.
Frances Karttunen:
TLĀ introductory particle for clauses expressing wishes, commands, admonitions; negative form: TLĀCA –TLĀCAMŌ let it be that / particular que se junta al imperative y al optativo; indica mas cortesía, mas insistencia que ma (S) TLĀ may substitute for MĀ as a clause introductory particle and conveys greater courtesy and deference. T and Z have TLA- ‘if should it be that, perhaps’, which can be identified both with this and with INTLĀ ‘if’, which is abundantly attested in B and C. See MĀ.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 250.
Lockhart’s Nahuatl as Written:
Attestations from sources in English:
1) optitive: like ma, to express desire (let), but with more of an element of chance, hope
2) imperative: precedes the command sometimes
3) conditional: in this form it is really yntla or intla (if), that sometimes has lost the -in or -yn
Robert Haskett and Stephanie Wood's notes from Nahuatl sessions with James Lockhart and subsequent research.