 Phonotactics is concerned with the freedoms and restrictions in the combinations of phonemes. Simply put, not every sequence of phones is possible in a language. Phonotactic constraints restrict permissible syllable structures where certain sounds can occur in the syllable and which sounds can proceed and follow certain other sounds. These constraints are highly language-specific, as shown in the permissible syllable structures in Hawaiian, Japanese, Korean, and English. The permissible types of phonemes that can appear in specific positions in the syllable also vary by language. Whereas in English, no syllable begins with a velar nasal consonant, even though it can occur at the end, other languages are not similarly constrained. Wolaf, for instance, contains syllables such as nem. Lastly, different languages have different restrictions regarding specific sound sequences. In German, knö may occur syllable initially. In present-day English, you won't find this sound sequence in the syllable onset. In summary, language-specific phonotactic constraints restrict permissible syllable structures where certain sounds can occur in the syllable and which sounds can proceed and follow certain other sounds.