Latin. Linguist Peter R. Petrucci proposes that Romanian loanwords containing "f" in place of the Proto-Slavic "x" were modelled on Macedonian patterns, because Proto-Slavic "x" developed into "v" in Macedonian in word-final position and after "u". According to Mallinson, "x" changed to "v" at a relatively late period of the development of Daco-Romanian, because Istro-Romanian retained the original "x" consonant. Petrucci proposes that the change of word-initial "v" to "h" in the Moldovan dialect of Daco-Romanian is to be attributed to Ukrainian influence either through language shift from Ukrainian or through the bilingualism of masses of Moldovans. One of the most interesting components of the Romanian phonological inventory is the vowel /ɨ/, which is the most recent addition to its inventory. Most linguists support that /ɨ/ first arose as an allophone of /ə/ in Romanian native vocabulary and not due Slavic influence as Petrucci argues that /ɨ/ cannot have come from Slavic *y as there is a lack of direct correspondence between Slavic loanwords and /ɨ/. Petrucci emphasizes that three of the earliest Slavic loanwords which now contain "î" could have originally contained /i/ in Romanian, because the vowel shift from /i/ to /ɨ/ is attested in similar position in some inherited words. Morphology Romanian is the sole Romance language still using the vocative case when addressing a person: domnule ("sir!"), Radule ("Radu!"), soro ("sister!"), Ano ("Anne!"). Unlike Latin, which used a distinct vocative ending only in the singular of one of the six classes of nouns, Romanian has three distinct vocative forms. The -e ending of masculine nouns in vocative corresponds to the specific Latin vocative suffix, but neither the -o vocative ending of feminine nouns, nor the -lor ending of plural forms can be detected in Latin. Since the vocative also exists in Slavic languages, linguists agree that contacts with Slavic-speaking groups enabled its preservation in Romanian, with some even suggesting that the vocative case (re-)appeared in Romanian as a consequence of a language shift from Slavic. Even if Common Romanian retained at least the traces of the vocative case, the vocative suffix of feminine nouns can most probably be attributed to the parlance of an originally Slavic-speaking group. The appearance of two forms of the infinitive, a short and a long form, is one of the distinctive features of Daco-Romanian and Istro-Romanian in comparison with other Romance languages. The shortening of the infinitive can also be detected