How does the root-and-pattern system work in Arabic?

In the root-and-pattern system, which is a characteristic feature of Afro-Asiatic languages, the meaning of a word is primarily conveyed by a sequence of consonants known as the root. This root identifies the general semantic field of the word, while the pattern—a specific arrangement of vowels and syllabic features—is interwoven with the root to provide grammatical information, such as tense, mood, or part of speech.123

For example, the Arabic root √ktb is associated with the concept of "writing". By applying different patterns to this root, the language creates various stems:12

• katab-: The past active stem (e.g., kataba, "he wrote").12
• kutib-: The past passive stem (e.g., kutib-a, "it was written").13
• -ktub-: The present active stem (e.g., ya-ktub-u, "he is writing").12
• kātib-: The active participial stem (e.g., kātib-un, "writing [one]").13

This system allows for complex morphological variations by modifying the internal structure of the word, often in combination with prefixes or suffixes, to express different grammatical contexts.124