A simple term may have no constituent part available for the proposed division, or it may have parts that do not separately signify portions of the intended meaning.
1. A term with no further linguistic part: the interrogative hamzah “أَ” is a single particle.
2. A term with letters that do not contribute component meanings: the letters of “Zayd” do not denote parts of Zayd himself.
Therefore, a simple term is not necessarily one letter long; and having several letters is not enough to make an expression logically compound.