Concord around ni, si and kuwa | Swahili Grammar

Swahili does not put all the work of “be” into one kind of word. Present affirmative ni and present negative si are invariable copulas, while finite forms of kuwa are verbs and therefore carry a subject marker. An adjective, demonstrative, possessive, or relative form elsewhere in the sentence continues to agree with its own controller independently.

That division of labor is the central fact: a copula does not absorb the concord of the words around it. English speakers are especially tempted to search for one form equivalent to is/are/was/were and then stop checking agreement. In Standard Swahili, every agreement target has to be checked at its own site. All unlabelled examples below are neutral in (informal) speech and (formal) writing.

Ni is present and invariable

In a basic present-time equation or description, ni has one form for every person and noun class. It can link a subject to a noun phrase or an adjective predicate.

Subject	Class	Copula	Agreeing predicate
mwanafunzi huyu	1	ni	mrefu
gari hili	5	ni	refu
vitabu hivi	8	ni	virefu
barua hizi	10	ni	ndefu

Mwanafunzi huyu ni mrefu na ni mchezaji mzuri wa mpira wa kikapu.

This student is tall and is a good basketball player.

Gari hili ni refu, kwa hiyo tutaliegesha nje.

This car is long, so we will park it outside.

Vitabu hivi ni virefu, lakini vina maelezo muhimu sana.

These books are long, but they contain very important explanations.

The parallel class 1, class 5, and class 8 descriptions keep ni unchanged. The demonstratives, predicate adjectives, and following finite verbs form three different concord chains: huyu—mrefu—a-, hili—refu—li-, and hivi—virefu—vi-.

With a nominal predicate, ni remains invariable as well: Asha ni daktari; Asha na Musa ni madaktari. Number belongs to the noun phrases, not to a supposed singular or plural form of ni.

Hiki ni kitabu changu, na hivi ni vitabu vya maktaba.

This is my book, and these are the library's books.

Here hiki/hivi, changu, and vya display class information; ni does not. For the full identification uses of the copula, see ni for identification.

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Do not ask “Which class form of ni do I need?” There is only ni. Ask instead which surrounding words are agreement targets and what controls each one.

Si is also invariable

The negative counterpart si likewise does not change for noun class in present copular predication. The predicate adjective still agrees.

Mti huu si mfupi; ni mrefu kuliko miti mingine bustanini.

This tree is not short; it is taller than the other trees in the garden.

Tunda hili si bichi; ni bivu na tamu.

This fruit is not unripe; it is ripe and sweet.

Viti hivi si vidogo; ni vikubwa vya kutosha kwa chumba hicho.

These chairs are not small; they are large enough for that room.

The invariant sequence is si in all three. Class 3 gives mfupi/mrefu, class 5 gives zero-concord forms bichi/bivu with these stems, and class 8 gives vidogo/vikubwa. A form can show zero visible prefix and still be the class-selected adjective form.

Si is not the same mechanism as a negative finite verb. Compare gari si jipya “the car is not new,” where si is the copula, with gari halijafika “the car has not arrived,” where class 5 appears in negative verbal marking. The negative copula guide develops that contrast.

Kuwa is an infinitive; finite kuwa carries subject concord

The citation form kuwa means “to be.” In an infinitive environment it begins with class 15 ku-; that ku- is part of the infinitival form rather than concord selected afresh by an outside noun. Once kuwa is finite, however, an ordinary subject-concord slot precedes tense or aspect marking.

Controller	Past	Future	Predicate adjective
mwanafunzi, class 1	alikuwa	atakuwa	mrefu
mti, class 3	ulikuwa	utakuwa	mrefu
gari, class 5	lilikuwa	litakuwa	refu
vitabu, class 8	vilikuwa	vitakuwa	virefu
barua, class 10	zilikuwa	zitakuwa	ndefu

Written normally, each finite verb is one word: li-li-kuwa is the explanatory analysis of lilikuwa, not its spelling. The first li- is class 5 subject concord; the second -li- is past tense. Similarly, vi-ta-kuwa is written vitakuwa.

Gari hili lilikuwa jipya tulipolinunua, lakini sasa ni kuukuu.

This car was new when we bought it, but now it is old.

Vitabu hivi vitakuwa muhimu kwa wanafunzi watakaoanza muhula ujao.

These books will be useful to the students who will begin next term.

The first example has class 5 hili—li-li-kuwa—jipya. The second has class 8 hivi—vi-ta-kuwa; muhimu is an invariable property word, so it does not acquire vi-. The agreeing and invariable systems coexist without contradiction.

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A finite kuwa contributes verbal subject concord; an agreeing predicate contributes adjective concord. In vitabu vilikuwa vizuri, the two vi- markers are selected independently by the same class 8 controller.

Negating finite kuwa

Past and future negation belongs to the verbal paradigm rather than to invariable si. The negative subject series appears on finite kuwa: hakuwa, halikuwa, havikuwa, and so forth. The predicate is still checked separately.

Sanduku halikuwa zito tulipolipokea, lakini sasa limejaa vitabu.

The box was not heavy when we received it, but now it is full of books.

Vifaa hivi havitakuwa vipya, lakini vitakuwa salama kutumia.

This equipment will not be new, but it will be safe to use.

In the second sentence, class 8 controls havi-ta-kuwa, vipya, and vi-ta-kuwa. Salama remains invariable. Do not replace a past or future negative finite form with si while leaving a tense meaning stranded.

Multiple controllers can occur around one copula

A copular clause can equate two noun phrases that have different classes. Each modifier agrees locally with its own noun; ni does not force the two phrases into one concord series.

Kitu hiki kidogo ni zawadi kubwa ya sherehe yetu.

This small thing is a major gift for our celebration.

Class 7 controls hiki kidogo. Class 9 zawadi controls kubwa ya. The clause is grammatical precisely because ni merely links the phrases; it does not impose class 7 on the predicate noun phrase.

This is another reason to work from controllers outward. In gari la mwalimu ni jipya, nearby mwalimu does not control jipya: the entire subject head is class 5 gari. But in gari ni zawadi mpya, class 9 zawadi is the head inside the nominal predicate and selects mpya. Structure, not distance from ni, decides.

Common Mistakes

Inventing class forms of ni or si

❌ Vitabu hivi vini vizuri.

Incorrect — ni has no class 8 form vini.

✅ Vitabu hivi ni vizuri.

These books are good.

Leaving the predicate adjective in the wrong class

❌ Gari hili si mpya.

Incorrect — class 5 gari requires jipya with the stem -pya.

✅ Gari hili si jipya.

This car is not new.

Treating finite kuwa as invariable

❌ Viti hivi ilikuwa vidogo zamani.

Incorrect — past kuwa needs class 8 subject marker vi-.

✅ Viti hivi vilikuwa vidogo zamani.

These chairs used to be small.

Repairing the copula but not the whole concord chain

❌ Magari hii mpya zilikuwa ndefu na ziliuzwa jana.

Incorrect — the dependents use class 9/10 forms instead of plural class 6 forms.

✅ Magari haya mapya yalikuwa marefu na yaliuzwa jana.

These new cars were long and were sold yesterday.

The controller magari requires haya, mapya, ya-li-kuwa, marefu, and ya-li-uzwa. The correction changes every dependent concord while leaving no class mark on an invented copula. This controller-outward repair is much safer than changing whichever prefix happens to sound closest.

Key Takeaways

Present ni and si are invariant. The infinitive kuwa is a citation form, but finite kuwa takes the subject concord required by its controller. Meanwhile, true predicate adjectives keep their own adjective concord, and invariable property words remain invariable. One clause can therefore contain no class mark on ni, a class mark on finite kuwa, and additional independent concords on predicates and modifiers.

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