Mapato ya mwezi yameongezeka.

Mapato usually means income, earnings, revenue, or proceeds. The best English translation depends on context:

• personal finances: income or earnings
• business context: revenue
• money received from something: proceeds

So in this sentence, it could refer to a person’s income or a company’s revenue.

Mapato is the common form you will usually see for income/revenue. It belongs to noun class 6, which often has the prefix ma-.

Even though pato exists, mapato is much more natural in everyday use when talking about income or revenue as a general concept.

Literally, ya mwezi means of the month.

In natural English, that can be understood as:

• monthly
• for the month
• the month’s

So mapato ya mwezi is something like the month’s income or monthly income/revenue.

Ya is the associative marker (often similar to of in English), and it must agree with the noun that comes before it.

Here, the noun is mapato, which is in noun class 6.
For class 6 nouns, the associative form is ya.

So:

• mapato ya mwezi = income of the month

If the first noun belonged to a different noun class, the associative marker would change.

Yameongezeka can be broken down like this:

• ya- = subject marker for noun class 6
• -me- = perfect aspect, often like has/have
• ongezeka = increase, go up, become greater

So yameongezeka means have increased or has increased, depending on how English expresses the subject.

Because mapato is the subject, the verb must use the class 6 subject marker ya-.

Because the verb must agree with mapato.

Mapato is a class 6 noun, so the verb takes the class 6 subject marker ya-:

• mapato yameongezeka

If the subject were a noun from another class, the verb marker would change.
So this is a matter of noun class agreement.

-me- usually expresses a completed action with present relevance. It is often similar to the English present perfect.

So yameongezeka suggests:

• the increase has already happened
• the result is true now

That is why it often translates naturally as has increased or have increased.

This is a very useful distinction:

• kuongezeka = to increase, to go up, to become greater
  
  • usually intransitive: the thing itself increases
• kuongeza = to increase something, to add, to raise
  
  • usually transitive: someone causes something to increase

In this sentence, mapato yameongezeka means the income has increased by itself as the subject of the sentence.

If you wanted to say someone increased the income, you would use a form of kuongeza instead.

It most naturally means income/revenue/earnings in a broad sense.

It can refer to:

• a person’s income
• a household’s earnings
• a company’s revenue

If you specifically mean salary, Swahili often uses mshahara instead.

So mapato is broader than salary.

Mwezi means month in the singular. Here it works in a phrase meaning of the month or monthly.

That is normal. Swahili does not need the plural here to express the idea.

Related forms:

• mwezi = month
• miezi = months
• mapato ya mwezi huu = this month’s income
• mapato ya kila mwezi = monthly income / income every month

So the singular mwezi is correct in this sentence.

Yes. This is a very normal Swahili sentence structure:

• Mapato ya mwezi = the subject
• yameongezeka = the verb

So the pattern is basically:

• Subject + Verb

Swahili often expresses ideas very compactly, and a sentence like this is completely natural without any extra words such as articles like the or a.