The article presents the analysis of the rules of punctuation concentrated on the use of a comma in Spanish language. Nevertheless, in the introduction the author cite several exemples to show the differences and similarities between the use of a comma in Spanish, Polish, Russian, Czech, French, English and German languages in order to emphasize the conventional nature of the comma. The main part of the work presents the use of a comma in Spanish in five syntactic contexts. The article ends with conclusions that reveal the obligatory, distinctive and optional nature of the comma in the Spanish orthography.