What is of interest in Sībawayh's analysis of ʔimālah is that he does not limit it to the overt and expressed contexts for ʔimālah but takes into account its absent, covert and unexpressed contexts. This obviously takes phonetics and phonology beyond the traditional limits of being sensitive only to what is expressed in the context and to no other.

In his discussion and analysis of ʔidγām ‘assimilation’, Sībawayh states that ʔal-ʔasʕlu fiy ʕ al-ʔidγām ʔ an yatbaʕa ʔal-ʔawwalu ʔal-ʔāxara ‘the principle of assimilation is that the first follow the other’ (II, P. 472, L. 17). This is his way of stating that the first becomes like the second or, more in harmony with current terminology, that assimilation is fundamentally regressive. If we were to consider ʔimālah ‘inclination’ a species of assimilation, then what applies to one is equally valid for the other. He illustrates this connection when he is discussing how ʔimālah ‘inclination’, as a process of changing [ā] to [ē] in the context of kasrah [i] or a yāʔ [y], is similar to the changing of the siyn [s] to a sʕād [sʕ] in the context of a Gāf [G] as in:

sabaGtu → sʕabaGtu ‘I preceded’ (II, P. 279, L. 18)

Sībawayh, in his discussion of ʔimālah, focuses on the contexts that trigger ʔimālah. In the process of his accounting for ʔimālah, he provides examples of a bidirectional process, that is, of progressive and regressive ʔimālah, where both the following or the preceding contexts determine ʔimālah, even if not all of his examples can be patently grouped under these two rubrics.