Phraseological units, set expressions with specialised non-literal meaning of the whole clearly represent the syntagmatic specificity of languages. Named cliches and ready-made expressions, these communicative units are easily recognized and decoded by people who have studied Latin, either in high school or university, but for students who encounter for the first time in the foreign language text (French, English) from the field of diplomacy and political science, the Latin phraseological units present one of the most difficult aspects of the discourse. Many authors give common current classifications to facilitate the consultation, the correct understanding and the proper use of the Latin expressions, especially in the works of practical character. Thus, in the small Latin-Romanian dictionary of commonly used expressions, authors discriminate among: commonly used words (alter ego – alternative self); word combinations (amor patriae – love of one’s country); aphorisms (festina lente – make haste slowly); proverbs, sayings of wide circulation (bis dat, qui cito dat – he gives twice who gives promptly).