Primum magistra verba difficilia interpretatur; tunc discipuli ea in margine scribunt.

Here primum is an adverb, not an adjective. It means first or first of all.

• primum = first, at first
• prima magistra would mean the first teacher or the female teacher who is first

So in this sentence, primum is not describing magistra. It is describing the whole action: First, the teacher interprets...

Latin does not have definite or indefinite articles.

So:

• magistra can mean teacher or the teacher
• discipuli can mean students or the students

You figure out whether English needs the or a/an from the context.

Magistra is in the nominative singular, which is the normal case for the subject.

Also, the verb interpretatur is third person singular, so it matches a singular subject:

• magistra = singular
• interpretatur = she interprets

So magistra is the one doing the action.

Because they agree with each other.

• verba is neuter plural accusative
• difficilia is also neuter plural accusative

Since difficilia describes verba, it must match it in:

• gender: neuter
• number: plural
• case: accusative

So verba difficilia means difficult words.

Because it is the direct object of interpretatur.

The teacher is interpreting the difficult words, so those words receive the action. In Latin, the direct object is usually put in the accusative case.

So:

• magistra = subject, nominative
• verba difficilia = direct object, accusative

Because interpretatur comes from a deponent verb.

The verb is interpretor, interpretari, which has:

• passive-looking forms
• but an active meaning

So:

• interpretatur looks passive
• but means she interprets, not she is interpreted

This is very common with deponent verbs in Latin.

Both are present tense.

• interpretatur = she interprets
• scribunt = they write

In a sentence like this, the present tense often describes a habitual action or a step-by-step classroom routine:

• first the teacher interprets
• then the students write

Because discipuli is nominative plural, and the verb scribunt is third person plural.

So they match:

• discipuli = students
• scribunt = they write

That tells you that the students are doing the writing.

Ea refers back to verba difficilia.

It means them or those things, and it is:

• neuter plural
• because verba is neuter plural

So the sentence is structured like this:

• teacher interprets the difficult words
• then the students write them

Because the pronoun must agree with the noun it refers to in gender and number.

The noun is verba:

• verbum is neuter
• plural: verba

So the matching accusative plural pronoun is ea.

Compare:

• masculine plural accusative: eos
• feminine plural accusative: eas
• neuter plural accusative: ea

Since verba is neuter plural, ea is correct.

It is accusative plural neuter.

Why accusative? Because it is the direct object of scribunt:

• the students write them

So ea is functioning just like them in English.

Because in takes different cases depending on the meaning.

• in + ablative = in/on a place, showing location
• in + accusative = into/onto a place, showing motion toward

Here the meaning is location: the students write in the margin, not into the margin.

So:

• in margine = in the margin
• margine is ablative singular

Because it follows in with the meaning of location.

The noun is margo, marginis. Its ablative singular is margine.

So:

• in margine = in the margin

This is a very common Latin pattern:

• in villa = in the house
• in urbe = in the city
• in margine = in the margin

Latin word order is much more flexible than English word order because the endings show each word’s job in the sentence.

English depends heavily on order:

• The teacher interprets the words

Latin can move words around more freely because case endings tell you what is subject and object.

In this sentence, the order is very natural Latin:

• Primum sets up the sequence
• magistra names the subject
• verba difficilia gives the object
• interpretatur comes at the end of the clause

Then the second clause does something similar:

• tunc = then
• discipuli = subject
• ea = object
• in margine = place
• scribunt = verb at the end

Yes, in the sense that both are adverbial words marking sequence.

• primum = first
• tunc = then

They help organize the actions in order. This is very common in instructional or narrative Latin:

• primum ...
• deinde ...
• tum/tunc ...
• postea ...

Scribunt is plural because the subject discipuli is plural.

• discipulus scribit = the student writes
• discipuli scribunt = the students write

So the ending -unt tells you the verb is third person plural.

Most likely it describes a routine or a typical sequence of actions, because both verbs are in the present tense and the sentence sounds instructional.

So it can be understood as:

• First the teacher interprets the difficult words; then the students write them in the margin

That is a very common use of the Latin present tense.