Tabellarius epistulam affert, quam mater statim legit.

It has two clauses:

• Tabellarius epistulam affert = the main clause
• quam mater statim legit = a relative clause

The relative clause adds more information about epistulam. In other words, it tells you something about the letter.

Tabellarius is nominative singular. It is the subject of affert, the one doing the bringing.

A native English speaker often expects word order to show the subject, but in Latin the ending is usually the main clue. Here -ius is the nominative singular ending of this noun.

Epistulam is accusative singular because it is the direct object of affert.

It answers the question What does the messenger bring?
Answer: epistulam.

So:

• tabellarius = subject
• epistulam = direct object

Quam is a relative pronoun, meaning which or that in this sentence.

It refers back to epistulam and connects the second clause to it. So the sense is:

• the letter
• which the mother immediately reads

Latin normally uses an explicit relative pronoun here, even where English might sometimes be looser.

Because quam is feminine singular accusative.

This happens for two reasons:

• It agrees in gender and number with its antecedent, epistulam, which is feminine singular.
• Its case comes from its job inside its own clause. In quam mater statim legit, it is the object of legit, so it must be accusative.

This is a very important Latin rule:

• a relative pronoun agrees with its antecedent in gender and number
• but gets its case from its own clause

Because mater is the subject of legit.

In the relative clause:

• quam = the thing being read
• mater = the person reading it

So mater must be nominative singular.

English speakers often expect the first noun after which to be the object or to follow a stricter word order, but Latin relies much more on case endings than on position.

Latin word order is much more flexible than English word order because Latin uses case endings to show each word’s function.

A few things are especially normal here:

• the relative pronoun quam often comes at the beginning of the relative clause
• the verb often comes later in the clause
• the adverb statim can be placed before the verb for a natural flow or emphasis

So Latin does not need to say things in exactly the same order as English does.

Statim is an adverb, and it modifies legit.

So it tells you when or how quickly the mother reads the letter: immediately, at once, right away.

It belongs with the second clause:

• quam mater statim legit

Affert is third person singular present active indicative of afferre.

So it means he brings, she brings, or it brings. Here the subject is tabellarius, so the meaning is the messenger brings.

The ending -t is the normal marker for third person singular in the present tense.

This is a very common question, because in ordinary spelling legit can be ambiguous.

With macrons, the difference is clearer:

• legit = reads
• lēgit = read or has read

In many Latin texts, macrons are not written, so you must use context to tell which tense is meant. In this sentence, since the meaning has already been given to the learner and the first verb affert is present, legit is understood as reads.

Classical Latin does not have articles like English the or a/an.

So:

• tabellarius can mean the messenger or a messenger
• epistulam can mean the letter or a letter

The context tells you which is more natural in translation. English requires an article, but Latin usually does not.