on-.

Headword: 
on-.
Principal English Translation: 

with numbers; functions like om- (two; also means and or plus)

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), 228.

Orthographic Variants: 
om-, o-
Attestations from sources in English: 

màtlāctli oncē = 11
Michel Launey, An Introduction to Classical Nahuatl, translated and adapted by Christopher MacKay (Cambridge: Cambridge University Press, 2011), 59.

màtlāctli onnāhui = 14
Michel Launey, An Introduction to Classical Nahuatl, translated and adapted by Christopher MacKay (Cambridge: Cambridge University Press, 2011), 59.

themes: 
Numbers, Math