وَأَمَّا اللَّفْظِيَّةُ: فَهِيَ أَنْ يَكُونَ الْمُضَافُ صِفَةً مُضَافَةً إِلَى مَعْمُولِهَا، وَهِيَ فِي تَقْدِيرِ الِانْفِصَالِ.
Translation: Formal iḍāfah occurs when the mudāf is a descriptive word attached to its own dependent and can be understood in an uncombined form.
A ṣifah is an active or descriptive derived word; a maʿmūl is the word governed or related to it.
Two adjacent nouns are not enough to identify formal iḍāfah: look for the governing relationship between a descriptor and its dependent.