The roots of verbs and most nouns in the Semitic languages are characterized as a sequence of consonants or "radicals" (hence the term consonantal root). Such abstract consonantal roots are used in the formation of actual words by adding the vowels and non-root consonants (or "transfixes") which go with a particular morphological category around the root consonants, in an appropriate way, generally following specific patterns. It is a peculiarity of Semitic linguistics that a large majority of these consonantal roots are triliterals (although there are a number of quadriliterals, and in some languages also biliterals).
Such roots are also common in other Afroasiatic languages. While Berber mostly has triconsonantal roots, Chadic, Omotic, and Cushitic have mostly biconsonantal roots, and Egyptian shows a mix of biconsonantal and triconsonantal roots.
A triliteral or triconsonantal root (שורש תלת־עיצורי, ; جذر ثلاثي, ; ܫܪܫܐ, ) is a root containing a sequence of three consonants.
The following are some of the forms which can be derived from the triconsonantal root k-t-b כ־ת־ב ك-ت-ب (general overall meaning "to write") in Hebrew and Arabic:
Note: The Hebrew fricatives stemming from begadkefat lenition are transcribed as "ḵ", "ṯ" and "ḇ", to retain their connection with the consonantal root כ־ת־ב k-t-b. They are pronounced x, θ, β in Biblical Hebrew and χ, t, v in Modern Hebrew respectively. Modern Hebrew has no gemination; where there was historically gemination, they are reduced to single consonants, with consonants in the begadkefat remaining the same.
In Hebrew grammatical terminology, the word binyan (בניין, plural binyanim) is used to refer to a verb derived stem or overall verb derivation pattern, while the word mishqal (or mishkal) is used to refer to a noun derivation pattern, and these words have gained some use in English-language linguistic terminology.