فالمفرد ما لا يقصد بجزئه الدلالة على جزء معناه
A simple expression is one whose part is not intended to signify a part of its intended whole meaning.
The restriction “is not intended” is crucial. A simple term need not lack physical parts: its parts may exist, and may even have independent meanings in other uses, but those meanings are not intended as components of the present signification.
“Zayd,” as a personal name, designates an individual. Its letters are not intended to indicate portions of that person, so the name is logically simple.