Final answer:
The type of writing that uses symbols to represent smaller units of sound is an alphabet. Alphabets use characters to denote vocal sounds and are exemplified by the Phoenician writing system, which significantly influenced the development of modern writing systems.
Step-by-step explanation:
The type of writing that uses symbols representing smaller units of sound is known as an alphabet. Unlike pictographic or logographic systems, which represent ideas or words, alphabetic systems use a set of characters to represent vocal sounds. For example, the Phoenician writing system, an ancestor of modern alphabets, developed around 1300 BCE, was based on a syllabic alphabet where characters correspond to sounds. This system eventually influenced the Greek and Roman alphabets, and by extension, the alphabets used in many languages today, including English. The English word "phonetic" describes a system where symbols correspond to sounds and is derived from "Phoenician."