Puer canistrum plenum fert; in eo catinus parvus et duo mala sunt.

Because puer is the subject of fert.

• puer = boy
• It is in the nominative singular, the case normally used for the subject of a sentence.
• So puer fert means the boy carries.

This is also a good reminder that Latin often shows grammatical function by case endings, not by word order alone.

Because canistrum is the direct object of fert.

• fert = carries
• The thing being carried is the basket, so canistrum is in the accusative singular.
• canistrum is a neuter second-declension noun, and its nominative and accusative singular are both -um.

So:

• puer = subject, nominative
• canistrum = direct object, accusative

Because plenum must agree with canistrum.

Latin adjectives agree with the nouns they describe in:

• gender
• number
• case

Here:

• canistrum is neuter
• singular
• accusative

So the adjective must also be neuter singular accusative:

• plenum = full

That is why Latin says canistrum plenum.

Here it is simply an adjective modifying canistrum.

So canistrum plenum means a full basket or the full basket, depending on context.

It is not a separate predicate like the basket is full. If Latin wanted to say that, it would usually need a form of esse:

• canistrum plenum est = the basket is full

But in your sentence, plenum stays attached to canistrum as part of the object.

Because Latin word order is much more flexible than English word order.

Both of these are normal:

• canistrum plenum
• plenum canistrum

And both mean the same thing.

Latin often places adjectives after nouns, but that is not a strict rule. Word order can also be used for:

• emphasis
• style
• rhythm
• clarity

So a learner should not assume that adjective position changes the basic grammar. The endings matter more than the position.

Because the verb is fero, ferre, tuli, latum = to carry, bear.

Its present tense third-person singular is:

• fert = he/she/it carries

This verb is a little irregular, so its forms do not always look like a regular third-conjugation verb.

Here the subject is singular:

• puer = one boy

So the verb must also be singular:

• fert = carries

eo is ablative singular of the pronoun is, ea, id = he, she, it; this, that.

Here it refers back to canistrum, which is neuter singular, so the correct pronoun form is eo in the ablative.

The phrase in eo means in it.

Why ablative? Because with in, Latin uses:

• ablative for location: in eo = in it
• accusative for motion into: in eum = into it

So here the sense is location, not movement.

Because Latin, like English, often uses a pronoun to avoid repeating a noun.

Instead of saying something like in canistro, the sentence says in eo = in it.

That is very natural. It links the second clause back to the basket already mentioned.

A learner should notice that Latin often uses is, ea, id as a simple third-person pronoun:

• eo = in it
• referring back to canistrum

Because the full subject of the second clause is actually compound:

• catinus parvus
• et duo mala

Together they make a plural idea:

• a small bowl and two apples

So the verb must be plural:

• sunt = are

Even though catinus parvus by itself is singular, the addition of et duo mala makes the whole subject plural.

Because duo must agree with mala.

Here mala is:

• neuter
• plural
• nominative

So the numeral must also take the matching form:

• duo = masculine/neuter nominative plural
• duae = feminine nominative plural

Since malum meaning apple is neuter, Latin says:

• duo mala = two apples

Not:

• duae mala — wrong gender
• duos malos — wrong case and wrong noun form

This is a very common beginner question.

malum meaning apple is a neuter second-declension noun.

Its forms include:

• singular nominative: malum
• plural nominative: mala

Neuter second-declension nouns have:

• singular nominative/accusative in -um
• plural nominative/accusative in -a

So mala here is not first declension. It is the normal neuter plural form of malum.

Yes, from the context.

Latin has two different words that can look similar:

• malum, mali = apple or apple tree fruit
• malum, mali = evil, bad thing

They are different words, even though some forms look identical.

In this sentence, the setting is a basket with a bowl and two mala, so apples is clearly the intended meaning.

Latin often simply uses a form of esse = to be.

So:

• catinus parvus et duo mala sunt literally = a small bowl and two apples are naturally = there is a small bowl and two apples / there are a small bowl and two apples

Latin does not need a separate dummy word like English there.

The existence idea is understood from the context and the verb sunt.

Because classical Latin has no articles.

So a noun like puer can mean:

• the boy
• a boy

And canistrum can mean:

• the basket
• a basket

Context tells you which is most natural in English.

That is why a translation may add the or a, even though no Latin word directly corresponds to them.

It has two clauses joined by punctuation:

1. Puer canistrum plenum fert

   • subject: puer
   • object: canistrum
   • adjective modifying the object: plenum
   • verb: fert

2. in eo catinus parvus et duo mala sunt

   • prepositional phrase: in eo
   • compound subject: catinus parvus et duo mala
   • verb: sunt

So the sentence moves from:

• the boy carrying the basket

to

• what is inside the basket

That kind of structure is very common in simple Latin prose.