Headword:
o-.
Principal English Translation:
a past tense indicator
Lockhart’s Nahuatl as Written:
"In texts of the sixteenth and early seventeenth centuries, o is optional with the preterit. After having seen many examples, it seems to me that the version without o tends to be the simple past, and the version with o a perfect: quimicti in iyaouh = He killed his enemy[;] oquimicti in iyaouh = He has killed his enemy.
Nevertheless, no certainty has been attained in this matter, and translations should follow the context. Usage seems to have varied from speaker to speaker, region to region, and above all over time. O became ever less optional; in texts of the eighteenth century you will hardly find a preterit without o." (p. 35)