In addition to monophthongs, Italian has diphthongs, but these are both phonemically and phonetically simply combinations of the other vowels, with some being very common (e.g. ), others being rarer (e.g. ) and some never occurring within native Italian words (e.g. ). None of these diphthongs are however considered to have distinct phonemic status because their constituents do not behave differently than they would in isolation (and all occur in isolation), unlike the diphthongs in some languages like English and German. Grammatical tradition makes a distinction between 'falling' and 'rising' diphthongs; however, since rising diphthongs are composed of one semiconsonantal sound or and one vowel sound, they are not actually diphthongs. The practice of referring to them as 'diphthongs' has been criticised by phoneticians like Luciano Canepari.