«ثلاثة» اسم خاص وضع لعدد معلوم.
“Thalathah” is a particular expression assigned to a definite number.
Thalathah means “three”; it cannot simply be read as an indeterminate or variable number. In thalathatu ayyam (“three days”), the number remains three, although additional conditions governing the days may be established elsewhere.
The methodological lesson concerns the precise numerical signification of a particular expression.