تمييز الكلام الفصيح عن غيره
Discriminating fasih speech from non-fasih speech.
It is not enough that a sentence conveys some intelligible content. One must also assess whether its words are jarring or unduly obscure, whether its grammar is weak, and whether its arrangement obstructs ready access to the meaning.
For instance, a familiar and contextually fitting message can still be deficient through syntactic weakness (daʿf al-taʾlif). Likewise, needlessly rare or awkward-to-pronounce words may diminish linguistic fluency. Understanding the relevant defects of fasaha is therefore one foundation of balagha.