and *dz, developed through a series of palatalizations that happened during the Proto-Slavic period, from earlier sequences either of velar consonants followed by front vowels (e.g. *ke, *ki, *ge, *gi, *xe, and *xi), or of various consonants followed by *j (e.g. *tj, *dj, *sj, *zj, *rj, *lj, *kj, and *gj, where *j is the palatal approximant (, the sound of the English letter "y" in "yes" or "you"). The biggest change in this inventory results from a further general palatalization occurring near the end of the Common Slavic period, where all consonants became palatalized before front vowels. This produced a large number of new palatalized (or "soft") sounds, which formed pairs with the corresponding non-palatalized (or "hard") consonants and absorbed the existing palatalized sounds . These sounds were best preserved in Russian but were lost to varying degrees in other languages (particularly Czech and Slovak). The following table shows the inventory of modern Russian: This general process of palatalization did not occur in Serbo-Croatian and Slovenian. As a result, the modern consonant inventory of these languages is nearly identical to the Late Common Slavic inventory. Late Common Slavic tolerated relatively few consonant clusters. However, as a result of the loss of certain formerly present vowels (the weak yers), Vowels A typical vowel inventory is as follows: The sound occurs only in some languages (Russian and Belarusian), and even in these languages, it is unclear whether it is its own phoneme or an allophone of /i/. Nonetheless, it is a quite prominent and noticeable characteristic of the languages in which it is present. Russian and Polish "mouse" Common Slavic also had two nasal vowels: *ę and *ǫ . However, these are preserved only in modern Polish (along with a few lesser-known dialects and microlanguages; see Yus for more details). Polish and "snake, snakes" Other phonemic vowels are found in certain languages (e.g. the schwa in Bulgarian and Slovenian, distinct high-mid and low-mid vowels in Slovenian, and the lax front vowel in Ukrainian). Length, accent, and tone An area of great difference among Slavic languages is that of prosody (i.e. syllabic distinctions such as vowel length, accent, and tone). Common Slavic had a complex system of prosody, inherited with little change from Proto-Indo-European. This consisted of phonemic vowel length and a free, mobile pitch accent: All vowels could occur either short or long, and this was phonemic (it could not automatically be