Syllables in Māori have one of the following forms: V, VV, CV, CVV. This set of four can be summarised by the notation, (C)V(V), in which the segments in parentheses may or may not be present. A syllable cannot begin with two consonant sounds (the digraphs "ng" and "wh" represent single consonant sounds), and cannot end in a consonant, although some speakers may occasionally devoice a final vowel. All possible CV combinations are grammatical, though "wo", "who", "wu", and "whu" occur only in a few loanwords from English such as "wuru", "wool" and "whutuporo", "football".