Infinitives as Abstract Nouns
The Swahili ku- prefix does more than just translate to the English "to" (as in "to read"). It creates a true verbal noun, or gerund, belonging to Noun Class 15. This means words like kusoma act as abstract nouns ("reading" or "the act of reading") that can be the subject or object of a sentence.
How It Works
Understanding the Class 15 nominalized infinitive is crucial to building natural Swahili sentences.
Morphology and Structure:
- Consonant stems: Simply attach ku- (soma → kusoma).
- Vowel stems: The prefix is generally ku- for vowel stems (kuimba, kuelewa). The use of kw- is a historical exception limited to specific verbs like kwenda and kwisha.
- Monosyllabic verbs: Verbs with one syllable retain the ku- prefix to maintain stress (kula = eating/to eat).
- Object Concords and Reflexives: An object prefix or the reflexive infix -ji- (e.g., kujifunza = learning, kujipenda = loving oneself) can be inserted directly before the verb root (kumpenda = loving him/her). The ku- prefix is retained when adding an object concord to an infinitive (e.g., kusoma → kukisoma). Note that phonetic changes occur when inserting certain object concords before vowel-stem verbs (e.g., ku- + m- + ona = kumwona). For monosyllabic verbs, the ku- is the infinitive prefix, and the object concord is simply inserted between this prefix and the verb root (e.g., "to eat it" is ku-ki-la → kukila).
- Negation: Insert the affix -to- to form the negative (kutosoma = not reading). Note that monosyllabic verbs attach -to- to the full positive infinitive to maintain stress (kutokula = not eating).
Class 15 Concords:
As abstract nouns, infinitives have no plural form and take Class 15 agreement markers. As a helpful mnemonic, note that Class 15 shares the exact same agreement markers (concords, demonstratives, possessives) as Class 17:
- Subject Prefix: ku-
- Possessive Prefix: kw- (e.g., kusoma kwangu = my reading; kuimba kwake = his/her singing)
- Adjective Prefix: ku-
- Demonstratives: huku, huko, kule
- Relative Infix: -ko-
- Object Infix: -ku-
Manner and Instrument:
Infinitives are frequently paired with the multipurpose preposition kwa to express how something is done (e.g., kwa kusoma = by reading).
Crucial Distinctions:
Do not confuse the Class 15 gerund with the Simultaneous -ki- (used for "while doing"), the General Place ku- (Class 17), the Past Negative -ku-, or the Second-Person Object -ku-. Be careful of homophony ambiguity here: a word like ninakutaka can mean "I want it" (Class 15 object) or "I want you" (second-person singular object).
Usage Note: English speakers often overuse the infinitive for phrases like "I want you to go." In Swahili, when the subject changes, you must use the Subjunctive -e (Nataka uende), not the infinitive.
Beginning and Loan Verbs:
The infinitive of -anza (begin) is kuanza; kwanza means “first/firstly” and is not its regular infinitive. Loan stems keep their lexical final vowels after ku-: kujibu (answering), kufikiri (thinking) and kusamehe (forgiving). These can function as Class 15 subjects just like kusoma.
Examples (5)
- Kusoma vitabu ni kuzuri.
Reading books is good.
Word by Word: To-read books is good.
Demonstrates the infinitive acting as a subject and triggering the Class 15 adjective agreement on '-zuri'.
- Kutojua huku kunanisumbua.
This not-knowing (ignorance) bothers me.
Word by Word: To-not-know this it-me-bothers.
Shows the negative infinitive taking the Class 15 demonstrative 'huku' and the Class 15 subject concord 'ku-' on the main verb.
- Alikataa kumpa pesa.
He refused to give him money.
Word by Word: He-past-refuse to-him-give money.
Demonstrates the infinitive acting as an object complement, housing the object concord '-m-'.
- Kuimba kwake kunafurahisha.
His/her singing is pleasing.
Word by Word: To-sing his/her it-pleases.
Shows the infinitive modified by a possessive pronoun, which must take the Class 15 'kw-' agreement.
- Kula sana si kuzuri.
Eating a lot is not good.
Word by Word: To-eat a-lot is-not good.
Demonstrates a monosyllabic verb acting as a noun phrase subject.
Common Mistakes
Failing to use Class 15 agreement for modifiers.
Kusoma nzuri.Kusoma kuzuri.Because 'kusoma' is a Class 15 noun, adjectives must take the 'ku-' prefix, not the N-class 'n-/m-' prefix.
Using the infinitive instead of the subjunctive when subjects change.
Nataka wewe kwenda.Nataka uende.Swahili requires the subjunctive, not the infinitive, after verbs of wanting or ordering when the person doing the action changes.
How It Connects
Learn This First
To understand nominalized infinitives, you must first be comfortable with the basic infinitive form (Class 15) and how it functions as a noun class. This includes knowing how to apply subject agreement and associative markers ('of') to the KU- class.
- ku- (ngeli ya 15)Class 15 Subject Agreement
When a nominalized infinitive acts as a subject, it requires the Class 15 subject marker 'ku-' for verb agreement.
Level 2 - -aOf and Association with -a
Nominalized infinitives often take modifiers using the associative '-a' (e.g., 'kusema kwao'), which requires understanding how nouns relate to other words.
Level 1
Related Patterns
- Infinitive Class 15
Provides the foundational overview of Noun Class 15, which houses these nominalized infinitives.
Foundations - kuto-Negative Infinitive with Kuto-
Details the specific mechanics of negating these verbal nouns using the -to- infix.
Level 4 - -eSubjunctive -e
Contrasts with the infinitive, showing what to use when expressing desires or commands involving a change of subject.
Level 3 - ku- (mahali)General Place Ku-
Helps distinguish Class 15 infinitives from Class 17 locatives, which look identical but serve a different function.
Level 2
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