Infinitive and Verbal Nouns (Ku-) in Swahili

Overview

The infinitive prefix ku- transforms verb roots into noun-like forms that can serve as subjects, objects, or complements. At the CEFR B1 level, understanding ku- as both an infinitive marker and a noun class (class 15) deepens grammatical insight and enables more sophisticated sentence construction.

"Kusoma" means both "to read" and "reading" (the act of reading). As a class 15 noun, it takes ku- agreement: "Kusoma ni kuzuri" (Reading is good). This dual function makes ku- forms extremely versatile.

How It Works

Formation

ku- + verb root (for monosyllabic roots, ku- is always retained)

Infinitive	Meaning as verb	Meaning as noun
kusoma	to read	reading
kufanya	to do	doing
kulala	to sleep	sleeping
kwenda	to go	going
kula	to eat	eating

Functions

1. Subject: Kusoma ni kuzuri. (Reading is good.)
2. Object: Ninapenda kusafiri. (I like to travel.)
3. After preposition: Kabla ya kulala... (Before sleeping...)
4. After modal: Ninaweza kusoma. (I can read.)
5. Purpose: Amekuja kusoma. (He has come to study.)

Class 15 Agreement

Feature	Form	Example
Subject prefix	ku-	Kusoma kunaendelea. (Reading continues.)
Possessive	kwa	Kwa kusoma... (By reading...)
Adjective	ku-	Kusoma ni kuzuri. (Reading is good.)

Examples in Context

Swahili	English	Note
Kusoma ni kuzuri.	Reading is good.	Subject + class 15 adjective
Ninapenda kusafiri.	I like to travel.	Object infinitive
Kabla ya kulala, soma kitabu.	Before sleeping, read a book.	After preposition
Kufanya kazi kunachekesha.	Working is tiring.	Subject with ku- agreement
Amekuja kujifunza.	He has come to learn.	Purpose
Kwenda ni rahisi, kurudi ni ngumu.	Going is easy, returning is hard.	Contrast
Kula vizuri ni muhimu.	Eating well is important.	Subject
Hatuwezi kumaliza leo.	We cannot finish today.	After modal

Common Mistakes

Dropping ku- from monosyllabic infinitives

• Wrong: Ninapenda la. (I like eat.)
• Right: Ninapenda kula. (I like to eat.)
• Why: Monosyllabic roots always retain ku-.

Using wrong class agreement for infinitive subjects

• Wrong: Kusoma ni nzuri. (Reading is nice — class 9 adjective)
• Right: Kusoma ni kuzuri. (Reading is good — class 15 adjective)
• Why: Infinitive nouns are class 15 and require ku- agreement.

Usage Notes

Infinitives after "kabla ya" (before) and "baada ya" (after) are the standard construction for temporal clauses in everyday speech. This is simpler than using full finite clauses and is preferred in most contexts.

Practice Tips

1. Infinitive subjects: Write five sentences using infinitives as subjects with class 15 agreement.
2. Purpose clauses: Write five sentences using infinitives to express purpose: "Amekuja kusoma, nimekwenda kununua..."
3. After prepositions: Practice combining infinitives with kabla ya, baada ya, and badala ya (instead of).

Related Concepts

• Prerequisite: Present Tense (-na-) — understanding verb structure is necessary for forming infinitives
• Prerequisite: Remaining Noun Classes (5/6, 11/10, 15, 16-18) — class 15 is the infinitive class