وَالْمُطَلَّقَاتُ يَتَرَبَّصْنَ بِأَنْفُسِهِنَّ ثَلَاثَةَ قُرُوءٍ
Divorced women are to wait, concerning themselves, for three qurūʾ. (Qurʾan 2:228)
Thalāthata fixes the number three, but qurūʾ admits the meanings menstrual periods and periods of purity. The number alone therefore does not resolve every detail of how the waiting period is calculated. Interpretation must attend to the relevant language and legal evidence.