يُوصَفُ بِهَا الْمُفْرَدُ
An individual word may be described as fasih.
كَلِمَةٌ فَصِيحَةٌ
A fasih word.
Here mufrad means an individual word considered as a word, not necessarily the singular as opposed to the grammatical plural. Its fasaha will concern phonetic form, familiarity, and established linguistic patterns.
This statement evaluates a word, not automatically an entire sentence or the person speaking it. A suitable word can still occur in a deficient expression.