1. Take off the final vowel on the infinitive, and if the nearest remaining vowel is a, i, or u, then then causative extension takes the form -isha
- Kurudi -> kurud + isha = kurudisha (To cause to return, to bring back) (Ali anarudisha vitabu - Ali is bringing back the books)
- Kuzama (To drown) --> kuzam + isha = kuzamisha (To cause to drown, to sink). (Upepo umezamisha meli -The storm caused the ship to sink)
2. If the nearest remaining vowel is e or o, then the causative extension takes the form -esha
- Kusoma -> Kusom + esha = kusomesha (To cause to study, teach) (Mwalimu huyu anasomesha Kiswahili (This teacher teaches Swahili)
3. Most verbs whose roots ends in -k undergo a slight modification when the causative extension is added. The -k changes to -sh and no further syllable is added
-Kukumbuka -> kukumbusha (To remember -> to make remember). Picha hii inanikumbusha zamani (This picture reminds me of the past)
(Note that the common verbs kuandika and kucheka are exceptions, their causative forms are kuandikisha (to register) and kuchekesha (to make laugh, to amuse)
4. Some verbs insert a -z- in their causative forms, while the verb kulala changes its last consonant to -z. Also, if a verb root ends in -n, the causative is formed with -ny-
- Kuuma -> kuumiza
- Kulala -> kulaza
- Kupona -> kuponya
5. You can also form causative verbs from adjectives and nouns. Simply take off the final vowel, and add -isha if the nearest remaining vowel is a/i/u or -esha if the nearest remaining vowel is o/e
- -safi -> kusafisha (clean -> to clean)
- -bora -> kuboresha