Mwalimu alisema ati tahajia ya neno hili ni rahisi ukihesabu herufi zake vizuri.

Here ati introduces reported speech, so it works a lot like that in English:

• Mwalimu alisema ati ... = The teacher said that ...

In many varieties of Swahili, ati is common in everyday speech. Depending on context, it can also suggest hearsay, quotation, or even a slightly skeptical so-called / supposedly, but in this sentence it simply introduces what the teacher said.

Both ati and kwamba can mean that when introducing a clause.

A rough difference is:

• kwamba = more neutral, standard, often more formal
• ati = very common in speech, often more conversational

So this sentence could also be said with kwamba:

• Mwalimu alisema kwamba tahajia ya neno hili ni rahisi...

That would still be correct. The choice of ati gives it a more spoken feel.

Alisema can be broken into:

• a- = he/she
• -li- = past tense
• -sema = say

So alisema means he said or she said.

Because mwalimu can refer to a male or female teacher, alisema does not tell you the teacher’s gender by itself.

Tahajia means spelling.

So:

• tahajia ya neno hili = the spelling of this word

It refers to how a word is written letter by letter.

This is a possession/genitive structure:

• tahajia = spelling
• ya = of
• neno hili = this word

So literally:

• tahajia ya neno hili = spelling of this word

The connector ya agrees with tahajia, not with neno. This is very normal in Swahili: the first noun is followed by a linking word meaning of, and then the second noun.

Because neno belongs to noun class 5 in the singular, and the demonstrative must agree with that noun class.

So:

• neno hili = this word

Some other examples of the same pattern:

• jina hili = this name
• tunda hili = this fruit

Even though English just uses this, Swahili changes the form depending on the noun class.

Ni rahisi means is easy.

• ni = the copula is/are
• rahisi = easy

So:

• tahajia ya neno hili ni rahisi = the spelling of this word is easy

In English, is changes depending on the subject, but ni does not change that way.

Ukihesabu means if you count or when you count.

It breaks down like this:

• u- = you (singular), often also used in a general you/one sense
• -ki- = if / when
• -hesabu = count

So ukihesabu literally means something like:

• if you count
• when you count

In this sentence it is probably a general you, not necessarily one specific person. English often does the same thing with if you count carefully...

Not always. -ki- often covers both if and when, depending on context.

So ukihesabu herufi zake vizuri could be understood as:

• if you count its letters carefully
• when you count its letters carefully

In this sentence, English would most naturally use if, because the idea is that the spelling becomes easy under that condition.

Because herufi here means letters in the plural sense, and the possessive agrees with herufi, not with neno.

Breakdown:

• herufi = letter / letters
• za- = possessive agreement for the plural class here
• -ke = his/her/its

So:

• herufi zake = its letters

This may feel strange to an English speaker, because English focuses on the owner: its. Swahili also marks agreement with the possessed noun itself. Since the thing possessed is letters, you get zake.

It refers to neno hili — this word.

So:

• herufi zake = its letters
• its = the word’s

The full idea is:

• count the letters of this word carefully

Vizuri means well, properly, or carefully, depending on context.

In this sentence it modifies ukihesabu:

• ukihesabu herufi zake vizuri = if you count its letters well/carefully

A natural English translation is carefully or properly, because the point is that accurate counting makes the spelling seem easy.

The word order is actually fairly close to English:

• Mwalimu alisema ati ... = The teacher said that ...
• tahajia ya neno hili = the spelling of this word
• ni rahisi = is easy
• ukihesabu herufi zake vizuri = if you count its letters carefully

Swahili often puts ideas in a very straightforward order, but it builds relationships differently:

• possession uses ya
• conditional/time clauses can be built directly into the verb with -ki-
• agreement shows up on demonstratives and possessives

So the sentence may look long, but each part is doing a clear grammatical job.

Yes, that is possible grammatically. Because of -ki-, both readings are available.

However, the most natural English choice depends on the meaning already intended:

• if you count its letters carefully emphasizes a condition
• when you count its letters carefully sounds more like something expected to happen

In this sentence, if is usually the better choice, because the teacher is saying the spelling is easy under that condition.