In combining into feet, the Watad has the precedence over the Sabab and the Fásilah, and again the Watad majmú’ over the Watad mafrúk. Hence the Prosodists distinguish between Ajzá aslíyah or primary feet (from Asl, root), in which this precedence is observed, and Ájzá far’íyah or secondary feet (from Far’ = branch), in which it is reversed. The former are four in number:—
1. Fa’ú.lun, consisting, as we have just seen of a Watad majmú’ followed by a Sabab khafíf, = the Latin Bacchíus (⏑ ‑ ‑).
2. Mafá.’í.lun, i.e. Watad majmú’ followed by two Sabab khafíf = the Latin Epitritus primus (⏑ ‑ ‑ ‑).
3. Mufá.’alatun, i.e. Watad majmú’ followed by Fásilah = the Latin Iambus followed by Anapaest (⏑ ‑ ⏑ ⏑ ‑).
4. Fá’i.lá.tun, i.e. Watad mafrúk followed by two Sabab khafíf = the Latin Epitritus secundus (‑ ⏑ ‑ ‑).
The number of the secondary feet increases to six, for as No. 2 and 4 contain two Sabab, they “branch out” into two derived feet each, according to both Sabab or only one changing place with regard to the Watad. They are:
5. Fá.’ilun, i.e. Sabab khafíf followed by Watad majmú’, = the Latin Creticus (‑ ⏑ ‑). The primary Fa’ú.lun becomes by transposition Lun.fa’ú. To bring this into conformity with a current derivative of fa’l, the initial Sabab must be made to contain the first letter of the root, and the Watad the two remaining ones in their proper order. Fá is therefore substituted for lun, and ’ilun for fa’ú, forming together the above Fá.’ilun. By similar substitutions, which it would be tedious to specify in each separate case, Mafá.’í.lun becomes:
6. Mus.taf.’ilun, for ’Í.lun.mafá, i.e. two Sabab khafíf, followed by Watad majmú’ = the Latin Epitritus tertius (‑ ‑ ⏑ ‑), or:
7. Fá.’ilá.tun, for Lun.mafá.’í, i.e. Watad majmú’ between two Sabab khafíf = the Latin Epitritus secundus (‑ ⏑ ‑ ‑).
8. Mutafá.’ilun (for ’Alatun.mufá, the reversed Mufá.’alatun) i.e. Fásilah followed by Watad majmú’ = the Latin Anapaest succeeded by Iambus (⏑ ⏑ ‑ ⏑ ‑). The last two secondary feet are transpositions of No. 4, Fá’.i lá.tun, namely: