Chai imemwagika juu ya meza.

Because Swahili verbs usually carry information about the subject and the tense/aspect.

In imemwagika:

• i- = the subject marker for the noun class of chai
• -me- = a completed/recent action, often similar to has/have
• mwagika = spill / be spilled

So imemwagika means something like has spilled or has been spilled / is spilled depending on context.

Using just mwagika by itself would be more like the dictionary form or an imperative-type form in other contexts, not the normal finite verb for this sentence.

The i- agrees with chai.

In Swahili, verbs usually match the noun they go with through a subject marker.
Chai belongs to the noun class that often uses i- in the singular.

So:

• Chai i-me-mwagika
• Tea it-has-spilled

Even though English does not show this kind of agreement very much, Swahili does it regularly.

This is a very common learner question.

• kumwaga = to spill something / to pour out something
  This is usually transitive, so it often has an object.
• kumwagika = to spill / to get spilled / to be spilled
  This is more intransitive, focusing on the thing that spilled.

So:

• Ameimwaga chai. = He/she has spilled the tea.
• Chai imemwagika. = The tea has spilled.

In your sentence, the focus is on the tea itself, not on the person who caused it.

It can overlap with all of those in English, depending on context.

The -me- tense/aspect usually shows a completed action with present relevance. So imemwagika often feels like:

• has spilled
• has been spilled
• is spilled

In natural English, the best translation depends on the situation.
If the meaning shown to the learner is something like The tea has spilled onto the table, that matches very well.

The important idea is that the spilling has already happened, and the result matters now.

Juu ya meza means on top of the table or simply on the table.

Breakdown:

• juu = top / upper part / above
• ya = a linking word, often translated loosely as of
• meza = table

So literally it is something like the top of the table.

In Swahili, this is a very common way to express location:

• juu ya meza = on the table
• chini ya meza = under the table
• karibu na meza = near the table

Because Swahili does not have articles like a, an, and the.

So meza can mean:

• a table
• the table

The exact meaning comes from context.

That is why juu ya meza can be translated as either:

• on a table
• on the table

In most real contexts, the situation tells you which one is meant.

Yes, in many contexts that sounds natural too.

• mezani means at the table / on the table / on the tabletop, depending on context.
• juu ya meza is more explicitly on top of the table.

So:

• Chai imemwagika juu ya meza = the tea has spilled on top of the table
• Chai imemwagika mezani = the tea has spilled on the table / at the table

Both can work, but juu ya meza is more visually specific.

Yes, though Swahili can sometimes be flexible.

The normal order here is:

• Chai = subject
• imemwagika = verb
• juu ya meza = location

So the sentence follows a common pattern:

Subject + Verb + Place

That makes it straightforward and natural.
If you changed the order, it might still be understandable in some contexts, but this version is the most standard for a learner.

Here, chai is treated as a singular mass noun, like tea in English.

You normally do not count it as separate individual items unless you mean servings or cups.
That is why the verb uses singular agreement:

• Chai imemwagika

If you were talking about multiple cups of tea, you would express that differently.

A helpful rough guide is:

ee-meh-mwa-GEE-ka

Some notes:

• i sounds like ee
• me sounds like meh
• mwa is pronounced together
• gi usually has a hard g, as in give
• stress in Swahili often falls near the second-to-last syllable, so -gi- is stressed here

So the whole sentence is roughly:

CHAI ee-meh-mwa-GEE-ka JOO-oo ya MEH-za

This is only an approximation for English speakers, but it is a useful start.

Yes, very often it does.

Using imemwagika tends to focus on the fact that the tea ended up spilled, often without emphasizing who did it. That can sound natural when something happened accidentally.

If you wanted to clearly say that someone spilled it, you would often use the transitive verb instead, for example with an explicit subject.

So this sentence naturally suits situations like:

• a cup tipped over
• tea leaked out
• tea got spilled onto the table

Yes, juu ya can sometimes mean above or over, depending on context.

But in this sentence, because the tea has spilled and the location is the table, the natural meaning is on the table or onto the table, not merely above the table.

So context decides the most natural English translation.