Derived stems are a morphological feature of verbs common to the Semitic languages. In those languages, the vocabulary is based predominately on roots consisting of three or four consonants, wherein each root may be the basis for a number of conceptually related words. Each language features a number of set patterns for deriving verb stems from a given root. Stems from the same root represent separate verbs, albeit often semantically related, and each is the basis for its own conjugational paradigm.
In each language, one stem is canonically associated with the ordinary active voice, while each of the others is canonically associated with the passive voice, the causative, the intensive, the reflexive, etc., or some combination thereof.
For example, both in Arabic and in Hebrew, many words that have a meaning related to writing contain the root K-T-B (in Hebrew, when the letter B does not come at the beginning of a word, it may sound like a V). Thus:In the basic stem, "he wrote" in Arabic is "huwa kataba", and in Hebrew it is "hu katav".
In a causative stem, "he dictated" - Ar: "huwa kattaba", Hb: "hu hikhtiv".
In the passive stem, "it was written" - Ar: "hatha inkataba", Hb: "ze nikhtav".
And in the reflexive stem of the intensive stem, "he corresponded" - Ar: "huwa takātaba", Hb: "hu hitkatev".
In each Semitic language, the number of common derived stems is different. In Hebrew there are seven common ones, in Arabic there are ten common forms and five rare ones, in Akkadian there are thirteen common patterns, and so on.
Derived stem Wikipedia
There are some ways for naming the stems themselves by their morphology. One is with a Latin letter. Another is with using the same root in all the stems; in Hebrew and Arabic, this root is P.ʕ.L / F.ʕ.L, that its meaning is related to "operated". (In Arabic, the letter P does not exist and in Hebrew it has both the sounds of P and of F). In some of the languages the stems are also numbered; in Arabic they are numbered, but in Hebrew they are not.G Stem is the Ground state. Ar: /faʕala/, stem #1. Hb: /paʕal/, also called Binyan Qal, meaning "the easy stem.
N Stem is the stem starting with the letter N. Ar: /Infaʕala/, stem #7. Hb: /nifʕal/. In both languages it is the passive voice form of G stem. In Arabic, this is the only passive voice stem that exists and in Hebrew, there other passive voice stems do not have an N as a prefix.
D Stem is the stem, in which the second letter of the root is doubled. Ar: /faʕʕala/, stem #2. Hb: /piʕel/ - the doubling variation from G Stem was changed to a vowel variation. In Arabic, this is the main causative stem. In Hebrew its main meaning (the neaning it has with the largest group of roots) is the intensive one, its secondary meaning is the causative and it has some more meanings. In Hebrew, the passive voice stem of D Stem is /puʕal/.
L Stem is the stem, in which the first vowel of the stem is long. Ar: /faaʕala/, stem #3. It is the main intensive Arabic stem. In Hebrew it does not exist. In Ge'ez language it has a "goal meaning".
Š Stem is the stem starting with the letter Š (sh), S, H, or ʔ (the glottal stop). Ar: /ʔafʕala/, stem #4. Hb: /hifʕil/. In both languages it has a causative meaning as the main meaning. In Hebrew it has a secondary meaning of state changing that fits the meaning of the Arabic 9th stem, /ʔifʕalla/. In Hebrew, the passive voice stem of Š Stem is /hufʕal/. In Hebrew, there is also a rare used stem - /šifʕel/ that means re-did.
T Stem (also called Gt) is the stem starting with the letter T. It has the reflexive meaning. Ar: /iftaʕala/, stem #8. In Hebrew, only one of its combinations exists.
Dt Stem is the combination of D Stem and T Stem, both in morphology and in meaning. Ar: /tafaʕʕala/, stem #5; reflexive-causative. Hb: /hitpaʕel/; reflexive-intensive.
Lt Stem is the combination of L Stem and T Stem. Ar: /tafaaʕala/, stem #6; reflexive-intensive.
Št Stem is the combination of Š Stem and T Stem. Ar: / Istafʕala /, stem #10; reflexive-causative. In Hebrew, this stem is a slang and rare.
Nt Stem is the combination of N Stem and T Stem. It exists in Akkadian language, Stem IV.2. In Aramaic language, the Nt Stem replaces both the N Stem and T Stem, Dtn replaces both Dn and Dt, and Štn replaces both Šn and Št.