The Decisive Verses (Al-Ayat al-Muhkamat) are the manifestations of the Meaning (Al-Ma'na), such as the form of the Name (Al-Ism). That is the Decisive which is beyond doubt, for He has fortified (ahkamaha), clarified, and honored them; thus they are 'Decisive'.
As for the Ambiguous Verses (Al-Mutashabihat), they are what He manifested of wives, children, paternal uncles, family, and relatives. They are the 'Ambiguous', according to the saying of the Exalted:
{As for those in whose hearts is deviation, they follow what is ambiguous of it} 1 ."
[187] It has been narrated through another path:
"The 'Ambiguous' (Al-Mutashabihat) are the Opposites (Al-Addad) who occupied the seats of the 'Decisive' (Al-Muhkamat), until their matter became confusing to the people of heedlessness, and they could not distinguish them from the Decisive."