Learn Hardcore Swahili: Mti huu unapendwa sana na watoto, kwa sababu kivuli chake kinatumiwa kuchezea. - This tree is greatly loved by the children, because its shade is used for playing.

na often means “and” or “with” in basic usage,
but in passive sentences, na is also used to introduce the agent (the “doer” of the action), like English “by”.

Examples:

Mti huu unapendwa na watoto = This tree is loved by children.
Chakula kililiwa na wageni = The food was eaten by the guests.

So na is the standard way to say “by [someone]” after a passive verb.

Why is it mti huu (“this tree”) and not huu mti?

Demonstratives in Swahili (this/that) normally follow the noun:

mti huu = this tree
mti ule = that tree (far)
kiti hiki = this chair
kitabu kile = that book

Putting huu before the noun (huu mti) is not the normal pattern in standard Swahili for simple “this/that” meaning. You mainly see pre-nominal demonstratives in other special patterns (like huyu hapa, yule yule) or in emphasis, but the basic, natural form is noun + demonstrative.

What is the difference between mti huu unapendwa sana na watoto and watoto wanapenda sana mti huu?

Both mean essentially the same thing, but the focus is different.

Watoto wanapenda sana mti huu = Children love this tree a lot.
Focus: children as the ones doing the loving (active voice).
Mti huu unapendwa sana na watoto = This tree is loved a lot by children.
Focus: the tree and its quality of being loved (passive voice).

In the given sentence, the tree is the topic and center of attention, so the passive form is preferred.

What does kivuli chake literally mean, and how is chake formed?

Kivuli chake literally means “its shade” (the tree’s shade).

kivuli = shade/shadow (noun class 7)
chake = “its / his / her” agreeing with class 7

Chake is built from:

cha- = possessive prefix for noun class 7 (ki-/vi- class)
-ke = his/her/its (3rd person singular)

So:

kivuli chake = its shade
kivuli changu = my shade
kivuli chao = their shade

The possessor here is the earlier-mentioned mti huu (this tree), so kivuli chake means “the shade of this tree / its shade.”

Could we say kivuli cha mti huu instead of kivuli chake? Is there a difference?

Yes, you can say kivuli cha mti huu, and it’s correct.

kivuli cha mti huu = the shade of this tree
kivuli chake = its shade (referring back to that tree)

Difference:

cha mti huu names the possessor explicitly (“of this tree”).
chake uses a pronoun (“its”), relying on context to know that “its” = the tree already mentioned.

In this sentence, kivuli chake is more natural because we already know we’re talking about that tree, so a pronoun works smoothly.

What does kinatumiwa mean, and how is it different from kinatumika?

Kinatumiwa means “is used” (someone uses it).

Breakdown:

ki- = subject prefix for noun class 7 (for kivuli)
-na- = present / habitual tense marker
tumi = from kutumia (“to use”)
-w- = passive marker
-a = final vowel

So kivuli chake kinatumiwa = “its shade is being used / is used”.

Kinatumika comes from the intransitive verb kutumika, which means “to be in use / to be usable / to function”.

kivuli kinatumika ~ “the shade is in use / serves a function.”

In your sentence, the idea is “children use its shade (for playing)”, so kinatumiwa (passive of “use [something]”) is the better choice.

Why is the subject prefix ki- in kinatumiwa and not i-?

Because kivuli belongs to noun class 7 (the ki-/vi- class).

Subject prefixes in the present tense:

Class 7 singular (ki- nouns, like kivuli, kitabu) → ki-
Class 9/10 (often N- nouns) → i-

So:

kivuli kinatumiwa = the shade is used.
meza inatumiwa = the table is used. (meza is class 9, so i-)

Using inatumiwa for kivuli would be incorrect agreement.

What does kuchezea mean, and how is it different from kucheza?

Both come from -cheza = “to play”.

kucheza = “to play” (general: play, dance, play games, etc.)
kuchezea = “to play on/with/in (something)” – it uses the applicative extension -e- / -ea, which adds the idea of a location, object, or instrument.

In kivuli chake kinatumiwa kuchezea:

kuchezea implies “to play in it / to play there (in that shade)”.
So literally: “its shade is used to-play-in/on (it).”

If you said:

kivuli chake kinatumiwa kucheza, it would be understood, but sounds less precise; kuchezea is more natural here because the shade is the place where they are playing.

Why is it kwa sababu and not just sababu for “because”?

Kwa sababu is the most common way to say “because” in standard Swahili.

Literally, kwa sababu = “for reason / due to the reason that…”
In practice, it works like the conjunction “because” before a whole clause.

Examples:

Ninachelewa kwa sababu kulikuwa na foleni. = I’m late because there was traffic.
Mti huu unapendwa sana na watoto, kwa sababu kivuli chake kinatumiwa kuchezea.

You may also see:

kwa sababu ya + noun = because of (something)
e.g. alilia kwa sababu ya maumivu = she cried because of the pain.
Or alternative connectors: maana, kwa kuwa, kwa vile (all meaning roughly “because / since”), with slightly different style or formality.

Where does sana go in the sentence, and could it be placed somewhere else?

Sana means “very / a lot / very much” and normally comes after the word it modifies.

In this sentence:

unapendwa sana = “is loved very much / is greatly loved”.

Typical placement:

Anapenda sana muziki. = He/she loves music a lot.
Wanafurahi sana. = They are very happy.

You wouldn’t normally put sana before the verb (sana unapendwa) in neutral, standard Swahili. The given position (right after unapendwa) is the natural one.

What is the overall structure of the sentence, in simpler parts?

The sentence can be seen as two linked clauses:

Mti huu unapendwa sana na watoto
→ This tree is loved very much by children.
kwa sababu kivuli chake kinatumiwa kuchezea
→ because its shade is used for playing (in it).

So the pattern is:

[Main statement], kwa sababu [reason clause].

This is a very common way to link a statement with its reason in Swahili.