How do broken plurals differ from sound plurals in Semitic languages?

In Semitic languages, the distinction between broken and sound plurals lies in how plurality is morphologically encoded within a noun or adjective.1

• Sound plurals are formed by adding a specific long-vowel suffix to the singular stem. This method is the predominant way of marking plurality across most Semitic languages.1
• Broken plurals are formed by modifying the internal pattern of the stem itself, rather than by attaching an external ending. This process is particularly common in Arabic, Ethiopic, and the South Arabian languages.1

Broken plural stems vary significantly in type. Some follow systematic, predictable configurations, such as the CaCāCiC- pattern used for stems with four consonants (e.g., the Arabic plural thaʿālib-u for thaʿlab-un "fox"). Others function as independent collective nouns, and some singular stems may even be associated with multiple possible plural forms to distinguish between different meanings. While broken plurals are most characteristic of the southern Semitic languages, residual traces in other languages suggest they were not historically limited to that region.1