This article contains IPA phonetic symbols. Without proper rendering support, you may see question marks, boxes, or other symbols instead of Unicode characters.
All Japanese vowels are pure—that is, there are no diphthongs. The only unusual vowel is the high back vowel /ɯ/ listen (help·info), which is like /u/, but compressed instead of rounded. Japanese has five vowels, and vowel length is phonemic, so each one has both a short and a long version.
Some Japanese consonants have several allophones, which may give the impression of a larger inventory of sounds. However, some of these allophones have since become phonemic. For example, in the Japanese language up to and including the first half of the twentieth century, the phonemic sequence /ti/ was palatalized and realized phonetically as [tɕi], approximately chi listen (help·info); however, now /ti/ and /tɕi/ are distinct, as evidenced by words like tī [tiː] "Western style tea" and chii [tɕii] "social status".
The "r" of the Japanese language (technically a lateral apical postalveolar flap), is of particular interest, sounding to most English speakers to be something between an "l" and a retroflex "r" depending on its position in a word. The "g" is also notable; unless it starts a sentence, most speakers pronounce it like the ng in "singer".
The syllabic structure and the phonotactics are very simple: the only consonant clusters allowed within a syllable consist of one of a subset of the consonants plus /j/. These type of clusters only occur in onsets. However, consonant clusters across syllables are allowed as long as the two consonants are a nasal followed by a homorganic consonant. Consonant length (gemination) is also phonemic.
source : wikipedia