Learn Hardcore Swahili: Sanduku hili ndimo tulimoweka barua jana usiku. - This box is where we put the letter last night.

It’s a cleft (focus) construction. The sentence puts special emphasis on the location: it highlights that it was specifically this box in which the letter was placed last night. A natural English rendering with the same focus is: It is in this box that we put the letter last night.

What exactly does ndimo mean, and how is it formed?

ndimo is a fused copular-locative form meaning roughly “it is in (there) that…”. Morphologically:

ni- = the copula “it is”
-mo = the locative morpheme “inside”
The consonant d is inserted for phonological reasons in these fused forms. So: ni + (d) + mo → ndimo. Use it to focus an interior location in a cleft.

How is ndimo different from ndipo and ndiko?

They all belong to the same family of focus-copula + locative:

ndimo = “it is inside (that) …” (interior of something)
ndipo = “it is at/then (that) …” (a specific place or time point)
ndiko = “it is there (that) …” (more general or distal place) Here, because we’re talking about the inside of a box, ndimo is the right choice.

Why is there a -mo inside the verb tulimoweka if we already have ndimo?

In this cleft pattern, the verb in the relative clause carries a matching locative marker to indicate “where.” So you get both:

ndimo to set up the focused location
-mo in the verb to mark the verb’s action as happening “in it” This redundancy is normal and expected in standard Swahili clefts.

Can I omit the -mo in the verb and just say … ndimo tuliweka barua …?

In careful Standard Swahili, keep the locative marker on the verb: … ndimo tulimoweka …. Dropping it is often judged incomplete or nonstandard. You’ll commonly see the same pattern with ndipo … alipokutana …, ndiko … walikofika …, etc., where the verb also bears the corresponding locative/relative marker.

How does tulimoweka break down morphologically?

tu- = we (subject marker)
-li- = past tense
-mo- = locative object “in it/inside”
weka = put Altogether: tu-li-mo-weka = “we put (it) in (there).”

Why is it ndimo and not ndilo, since “sanduku” is class 5?

Because the emphasis is on the location “inside the box,” not on the box as a simple noun referent. ndimo focuses the locative “inside,” whereas ndilo would agree with a class-5 noun and focus the noun itself (e.g., “this is the box that …”). To say “the one that (box) …” you’d use ndilo + a class-5 relative on the verb; to say “the place in which …” you use ndimo + the locative -mo on the verb.

Would Sanduku hili ndilo … ever be correct?

It can be, but it changes the structure and meaning. For example:

Sanduku hili ndilo tulilotumia kuweka barua jana usiku. = “This box is the one that we used to put the letter last night.” (Focus on the box as the noun) Your original sentence uses ndimo … tulimoweka … to focus the inside of the box as the place where the action occurred.

Could I use a simpler, non-cleft version?

Yes. For a neutral sentence without special focus:

Tuliweka barua katika/kwenye sanduku hili jana usiku. This says the same thing but without the cleft emphasis.

Can I replace ndimo with humo?

Humo = “inside there (in that thing)” and acts like a locative pronoun/adverb.
ndimo is the cleft form used to focus the location. You could say:
Humo tulimoweka barua jana usiku. = “We put the letter in there last night.” (No cleft, still uses -mo)
Humo ndimo tulimoweka barua jana usiku. = very emphatic (“It is right in there that we put …”) In your sentence, because you’re naming the box, Sanduku hili ndimo … is ideal.

What’s the difference between -po, -ko, and -mo again?

-po: a specific, definite place or time point (or surface/point-like location)
-ko: a general, distal, or less specific location
-mo: the inside/interior of something Since a box has an interior, -mo fits best.

What about the time phrase — is jana usiku the only way to say “last night”?

Both are common:

jana usiku (very common, conversational)
usiku wa jana (a bit more formal or careful) They’re interchangeable in most contexts.

Can I move the time phrase to the front?

Yes:

Jana usiku tuliweka barua katika/kwenye sanduku hili. With the cleft, you can also front time using ndipo:
Jana usiku ndipo tulimoweka barua katika sanduku hili. (Focusing the time: “It was last night that …”)

Why is there no article before barua? Is it “a letter” or “the letter”?

Swahili doesn’t use articles (a/the). barua can be interpreted as “a letter” or “the letter” depending on context. If you need to be explicit:

“a letter”: barua moja
“the letter” (already known in context): often just barua, or add ile (“that one”) if needed: barua ile

Is barua singular or plural here?

By form, barua (class 9/10) is the same in singular and plural. Context usually disambiguates. If you want to specify:

one letter: barua moja
two letters: barua mbili, etc.

Could I use tia instead of weka?

Often yes, especially with the sense “put into”:

… tulimoitia barua … or more commonly keep the structure and say: … tuliitia barua (ndani ya) sanduku hili … However, weka is the neutral, very common “put/place,” and fits perfectly here. tia can sound a bit more like “insert/put into.”

Is there a relative-clause alternative without the cleft?

Yes:

Sanduku hili ambamo tuliweka barua jana usiku. = “This is the box in which we put the letter last night.” Here ambamo means “in which,” matching the interior sense of -mo.