Idadi imefika bilioni moja.

Idadi means number, total, count, or quantity. In this sentence, it refers to the total figure or amount.

It is the right word when you are talking about how much something adds up to.

Idadi is about a quantity or total.

Nambari is usually a number used as an identifier, such as:

• a phone number
• a house number
• a page number

So if you mean the total has reached one billion, idadi is natural. Nambari would sound like you are talking about a label or code.

Imefika can be broken down as:

• i- = subject marker
• -me- = perfect marker
• -fika = arrive, reach

So imefika literally means something like it has reached or it has arrived at.

The subject is idadi, and it takes the class 9 subject marker i- in the singular.

So the verb agrees with idadi:

• idadi imefika

You would use a- with a person, for example:

• amefika = he/she has arrived

So imefika is correct because the subject is not a person; it is the noun idadi.

-Me- is a perfect marker. It often corresponds to English has/have + past participle.

So imefika means:

• has reached
• has now reached

It shows that the reaching has already happened and is relevant now.

Yes, the basic meaning of -fika is arrive or reach.

But in Swahili, just like in English, a verb of movement can be used figuratively. So a number, amount, or total can reach a certain level.

Here, idadi imefika bilioni moja means the total has reached the level of one billion.

Swahili often allows the target level or amount to come directly after -fika.

So:

• imefika bilioni moja

is a normal way to say it has reached one billion.

You may also hear imefikia bilioni moja, especially in more formal or careful style. Both express the idea of reaching that amount.

In Swahili, numbers usually come after the noun they describe.

So:

• bilioni moja = one billion
• bilioni mbili = two billion

That is why moja follows bilioni.

Usually, bilioni stays the same form whether you mean one or more than one. The number word shows the difference:

• bilioni moja = one billion
• bilioni mbili = two billion

This is common with many borrowed words in modern Swahili.

Swahili does not normally use articles like a, an, or the.

So idadi imefika bilioni moja can mean:

• the number has reached one billion
• a number has reached one billion

In real use, the context tells you which meaning is intended.