triliteral

In the terminology used to discuss the grammar of the Semitic languages and some other Afro-Asiatic languages, a triliteral (Arabic: جذر ثلاثي, ) is a root containing a sequence of three consonants (so also known as a triconsonantal root). The majority of consonantal roots in these languages are generally triliterals (but some may be quadriliterals). Such abstract consonantal roots are used in the derivation of actual words by adding the vowels and non-root consonants which go with a particular morphological category around the root consonants, in an appropriate way, generally following specific patterns.
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ثلاثى ،کلمه سه حرفى

triliteral
\tri*lit"er*al\ (?), a. [pref. tri- + literal.] consisting of three letters; trigrammic; as, a triliteral root or word. -- n. a triliteral word.

(n.)
A triliteral word.
  

(a.)
Consisting of three letters; trigrammic; as, a triliteral root or word.
  

adj. having three letters