Al-ʿaks reverses the order of parts of an expression in a later clause. The reversal produces a new relation or emphasizes an existing contrast.
«عَادَاتُ السَّادَاتِ سَادَاتُ الْعَادَاتِ»
“The habits of eminent people are the noblest of habits.”
In the first clause, ʿādāt is the first member and al-sādāt the second; in the second clause their positions are inverted. The reversal does more than repeat words: it intensifies praise of the habits described.