Stacked Verb Extensions

When stacking extensions, the syntactic roles change hierarchically. For example, adding an Applicative -ia makes the beneficiary the direct object, and adding a Passive -wa promotes that beneficiary to the subject. A clear progression looks like this: pika (cook) -> pikia (cook for) -> pikiwa (be cooked for).

Core Extensions:
The most common extensions you will stack are the Applicative (-ia/-ea), Causative (-isha/-esha or short -za/-ya), Passive (-wa, -iwa/-ewa), Stative (-ika/-eka), Reciprocal (-ana), and Reversive, which has a transitive/active form (-ua/-oa) and an intransitive/stative form (-uka/-oka).

Key Rules for Stacking:

• Order: A helpful baseline rule for learners is the CARP mnemonic: Causative, Applicative, Reciprocal, Passive. While Swahili extension order is primarily driven by the Semantic Scope Hypothesis (meaning the logic and intended meaning dictate the order of affixes), the passive extension is structurally fixed and almost universally sits at the very end, right before the final vowel. Note that some combinations are logically restricted; for instance, because the Passive demotes the original subject and promotes an object to subject, you generally cannot add an Applicative after a Passive.
• Vowel Harmony: Harmony rules apply primarily to Applicative, Stative, and Causative extensions. If the relevant preceding root vowel is e or o, these extensions take e. If that vowel is a, i, u, they take i. They never take o or u. However, the Reversive Extension only takes o if the root has o, and takes u for all other vowels (a, e, i, u). Furthermore, the Reciprocal -ana has a fixed vowel and is immune to harmony. Instead of breaking the harmony rules, it resets the harmony trigger: because it acts as an a vowel, any subsequent extensions will naturally take their i forms (e.g., -ania, -anisha).
• Epenthesis and Mutation: Verbs ending in two consecutive vowels (where the stem itself ends in a vowel before the final -a, such as nunu-a or ondo-a) insert an -l- before the stack to prevent vowel clashing. Most Arabic loan verbs ending in -i, -e, or -u (except those ending in -au) drop their final vowel and attach the extension according to standard vowel harmony based on the last remaining vowel in the stem (e.g., jaribu -> jarib- -> jaribia). Additionally, the short causative (-za or -ya) mutates the final consonant of the root or replaces the final vowel (e.g., lala -> laza). When attached to vowel-ending stems, the passive explicitly takes the Extended Passive Forms -liwa or -lewa (e.g., nunua -> nunuliwa, ondoa -> ondolewa).
• Monosyllabic Verbs: Short verbs (like la, ja, pa, nywa) often take specialized or longer extension forms (e.g., kula -> kuliwa, kulika, kulia) and bypass standard epenthesis rules.
• Double Extensions: Extensions can be doubled for intensive or specialized meanings, such as the Lexical Double Applicatives (-ilia / -elea) used to mean doing something thoroughly or completely (e.g., shika -> shikilia, tupa -> tupilia).
• Lexicalization (Idioms): Stacked extensions often create idiomatic meanings that cannot be perfectly deduced from their individual parts and must be memorized as new vocabulary. For example, sikia (hear) -> sikilizana (understand each other / get along).

Be careful not to confuse true stacks with single long extensions like the Causative -isha, or with base verbs that just happen to end in similar syllables (like ingia).

Loan Stems in -au:
Learn the extended forms of sahau: sahaulia (forget for/on someone’s behalf, according to context) and sahauliwa (be forgotten). The -l- appears in these longer forms; simply deleting final -u and applying the jaribu model misses this stem type. Different extensions have their own loan-stem patterns.