Voiceless vowels often become voiceless in European Portuguese. This happens with vowels that are unstressed and is very common at the end of words and in rapid speech. The vowels can also be completely deleted.
The words quatro (four), sete (seven) and escola (school) all have vowels that can be voiceless. In the word quatro, the final vowel can be voiceless or completely deleted. This is also the case with the final vowel of sete. In the word escola, the first vowel can be voiceless. When the vowels are voiceless, they are pronounced without vocal cord vibration.
In European Portuguese, voiceless vowels are very common. They also occur in varieties of Brazilian Portuguese, but they are a feature that is much more associated with European. The use of voiceless vowels is more common in the dialects of southern and central Portugal than in the northern ones.
