Japanese vowels are "pure" sounds, similar to their Italian or Spanish counterparts. The only unusual vowel is the high back vowel /ɯ/, which is like /u/, but unrounded. 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 of the first half of the twentieth century, /ti/ was palatalized to [tɕi], approximately chi; however, now /ti/ and /tɕi/ are distinct, as evidenced by words like paatii [paatii] "party" and chi [chi] "ground."

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 /y/. However, consonant clusters across syllables within the word are common, though limited in type.