The punctuation of 15th century printed matter in Portuguese was analyzed, using variable-rule methods taken from sociolinguistics, in order to identify the regularities that guided its use. At the time, only prescriptive statements about Latin punctuation were available as models. In late Latin grammars, punctuation was described as a device for marking cohesive relations witin the text. In the absence of both grammars and orthographic treatises for Portuguese, the punctuation of works printed in the vernacular used fewer signs than Latin, and the main effect of this was a reinterpretation of their functions. The sensus perfectus which had guided Latin punctuation gave way to punctuation in the vernacular with clause-delimiting function.
The analysis provides evidences: (a)that there were contexts in which punctuation systematically did or did not appear; (b)that the comma and the colon were used in the same contexts, but with different functions; (c) that the comma was being introduced for texts printed in the vernacular; (d) that usage became more regular over the period studied (1495-1518); and (e)that the orthographic sentence was born through these processes.