For this site, Old Latin is the name given to Latin from its first literary production with Livius Andronicus in c. 240 until the career of Cicero begins in 80 BCE. Latin from before this period is confined to inscriptions and is often called either Early Latin, Very Old Latin, or Archaic Latin, the latter of which is sometimes applied to both periods.
(With the first term, this site becomes a misnomer, as it covers Latin from Andronicus down through the imperial period.)
Of all the authors writing in this 160 year period, only works from three authors survive in full: the comic playwrights Plautus and Terence, and Cato the Elder, though only his De Agri Cultura. For the rest of the authors, we are reliant primarily on grammarians who quoted them for unusual forms, meanings, and idioms. There are also a number of inscriptions present.
Like all languages, the divisions are arbitrary and authors fall on an overlapping continuum. Certain spellings and forms differ between the periods, but really only at the ends, so that Andronicus is closer to Cato than he is to Cicero, but the difference between Cicero and Cato is much smaller than the difference between Cicero and Andronicus.
The real reason for the distinction is aesthetic: Cicero and later Caesar (and sometimes Catullus) came to represent the very epitome of Latinitas, of a good, polished, elite Latin style, that earlier Latin was thereafter labeled archaic. In reality, the two periods are nearly identical in vocabulary, syntax, and accidence, and any given person in one period would have been fully intelligible with someone else in the other.
- Charles E. Bennett, Syntax of Early Latin. Two volumes. Boston: Allyn and Bacon, 1910 & 1914.
- Sander M. Goldberg, “The Early Republic: the Beginnings to 90 BC,” in Stephen Harrison ed., A Companion to Latin Literature. Malden, MA: Blackwell Publishing, 2005.
- Sander M. Goldberg, “Antiquity’s Antiquity,” in Wim Verbaal, Yanick Maes, & Jan Papy eds., Latinitas Perennis Volume I: The Continuity of Latin Literature. Leiden: Brill, 2007.
- J. N. Adams & Nigel Vincent eds., Early and Late Latin: Continuity or Change? Cambridge: Cambridge University Press, 2016.