Sporta servi plenissima est, quia panem, caseum, et olivas portat.

Because servi is genitive singular, meaning of the slave. Latin uses the genitive case where English often uses of or an apostrophe-s.

So:

• servus = slave as the basic dictionary form
• servi = of the slave

That is why sporta servi means the slave’s basket or the basket of the slave.

By form alone, yes: servi can also be nominative plural, meaning slaves. But in this sentence it is almost certainly genitive singular.

Why?

Because sporta servi plenissima est makes good sense as the slave’s basket is very full. If you tried to read servi as slaves, you would get something awkward like the basket, the slaves, is very full, which does not fit the grammar or meaning.

So this is a good example of how Latin forms can sometimes be ambiguous until context makes the meaning clear.

Plenissima is the superlative form of plena, so literally it can mean fullest or most full. But in Latin, superlatives are often used where English would simply say very.

So here plenissima est is best understood as:

• is very full
• or more literally, is fullest

In normal English, very full sounds much more natural than fullest in this sentence.

Because it agrees with sporta.

Latin adjectives must match the noun they describe in:

• gender
• number
• case

Here:

• sporta is feminine
• singular
• nominative

So the adjective must also be feminine singular nominative:

• plenissima

It does not agree with servi, because servi is not the thing being described. The basket is full, not the slave.

They are direct objects of portat, so they are in the accusative case.

The verb portat means carries, and the things being carried are:

• panem = bread
• caseum = cheese
• olivas = olives

That is why they appear in accusative forms:

• panis → panem
• caseus → caseum
• oliva → olivas

A native English speaker often has to get used to the idea that Latin changes noun endings to show their job in the sentence.

The subject is understood from context. Latin often leaves out subject pronouns when the verb ending already tells you the person and number.

Portat means:

• he carries
• she carries
• it carries

The ending -t shows third person singular. Latin does not need to add he unless there is some special reason to emphasize it.

In this sentence, the understood subject is the slave, based on the meaning: the basket is very full because the slave is carrying bread, cheese, and olives.

Grammatically, the verb form itself could mean he/she/it carries, so the verb alone does not tell you whether the subject is a person or a thing.

But context solves the problem. A basket is not normally the thing doing the carrying; the slave is. So the natural reading is that the slave is carrying the food, which explains why the basket is very full.

If someone wanted to make the subject completely explicit, Latin could say servus panem, caseum, et olivas portat.

Quia means because. It introduces a clause giving the reason.

So the sentence is structured like this:

• Sporta servi plenissima est = the slave’s basket is very full
• quia panem, caseum, et olivas portat = because he carries bread, cheese, and olives

A learner should notice that quia works much like English because.

Latin word order is much more flexible than English word order because Latin uses endings to show grammatical relationships.

English depends heavily on position:

• The slave carries the bread

If you change the order too much in English, the meaning changes or becomes confusing.

Latin can move words around more freely because endings show what each word is doing. So:

• panem portat
• portat panem
• panem servus portat

can all still mean roughly the slave carries bread, depending on context.

In this sentence, Sporta servi plenissima est is perfectly natural Latin, even though an English speaker may expect a more rigid order.

Because Latin has no articles. There is no direct equivalent of English the or a/an as an ordinary part of the noun system.

So:

• sporta can mean a basket or the basket
• servi can mean of a slave or of the slave
• panem can mean bread or the bread, depending on context

When translating into English, you add the or a based on what sounds natural in the context.

Yes. That is the most literal way to understand it.

Latin very often expresses possession by putting the possessor in the genitive case:

• sporta servi = basket of the slave
• natural English: the slave’s basket

This is one of the most important uses of the genitive, and it is much more common in Latin than trying to imitate the English apostrophe-s directly.