Mater fenestras claudit, ne fulgur servos et infantes terreat.

Because fenestras is the direct object of claudit (closes). The mother is doing the action, and the windows are what she closes.

• fenestra = window
• fenestras = windows in the accusative plural

So:

• Mater = the subject
• fenestras = the thing being closed

Claudit is:

• 3rd person singular
• present tense
• active voice
• indicative mood

from claudere = to close

So mater fenestras claudit means the mother closes the windows or mother is closing the windows, depending on context.

The -t ending tells you the subject is he/she/it, and here that subject is mater.

Ne introduces a negative purpose clause.

In other words, it means:

• so that ... not
• or more naturally in English, lest

So:

• ne fulgur servos et infantes terreat = so that lightning may not frighten the slaves and children

This is a very common Latin pattern:

• ut = so that
• ne = so that not

Because it is in a purpose clause introduced by ne.

Latin normally uses the subjunctive after ut or ne when expressing purpose.

So the structure is:

• main clause: Mater fenestras claudit
• purpose clause: ne ... terreat

Terreat is the present subjunctive of terrere = to frighten

This does not mean the action is doubtful in the English sense. In Latin, the subjunctive is often required by the grammar of the clause, especially after ut/ne for purpose.

Because Latin normally uses ne for a negative purpose.

Compare:

• ut veniat = so that he may come
• ne veniat = so that he may not come

Latin usually does not say ut non for ordinary negative purpose. A learner often wants to translate English word-for-word, but Latin prefers ne by itself.

Because of both case and meaning.

In the clause:

• fulgur = nominative singular
• servos et infantes = accusative plural

That means:

• fulgur is the thing doing the frightening
• servos et infantes are the people being frightened

So:

• fulgur terreat servos et infantes = lightning may frighten the slaves and children

Also, terreat is 3rd person singular, which matches fulgur as a singular subject.

Fulgur is a neuter third-declension noun meaning lightning or a lightning flash/bolt.

A useful thing to notice is that many neuter nouns have the same form in the nominative and accusative singular. Here, however, context shows that fulgur is the subject, not the object.

So even if the form could look ambiguous by itself, the rest of the sentence makes its job clear.

Because both are direct objects of terreat.

The lightning may frighten:

• servos = the slaves
• infantes = the children

So Latin coordinates two objects with et:

• servos et infantes

Both are in the accusative because both receive the action of terreat.

Because infans, infantis is a third-declension noun.

Its accusative plural is infantes.

So:

• infans = child / infant
• infantes = children / infants

This is a good reminder that not all plural objects end the same way in Latin:

• second declension masculine accusative plural: -os → servos
• many third declension accusative plurals: -es → infantes

Because mater is a third-declension noun, not a first-declension one.

Its basic forms are:

• mater = mother
• matris = of the mother

So mater is the nominative singular subject of the sentence.

A native English speaker may expect a feminine noun to look like puella, but many feminine Latin nouns belong to other declensions, and mater is one of them.

Because the verb agrees with its subject, not with its objects.

Here the subject is:

• fulgur = lightning

That is singular, so the verb is singular:

• terreat = may frighten

The plural nouns:

• servos
• infantes

are objects, so they do not control the verb ending.

Because Latin word order is much freer than English word order, and verbs often come late, especially in subordinate clauses.

So:

• ne fulgur servos et infantes terreat

is a very natural Latin order.

Putting terreat at the end helps mark the clause neatly and can give a sense of completion. English usually needs a stricter order, but Latin often uses word order for emphasis or style rather than basic grammar.

It is a purpose clause, not a fear clause.

Why?

Because the main verb is an action done for a purpose:

• Mater fenestras claudit = mother closes the windows
• ne ... terreat = so that lightning may not frighten ...

A fear clause would usually come after a verb of fearing, such as timeo or vereor.

So this sentence means the mother closes the windows in order to prevent the frightening.

Because the main verb claudit is in a primary tense (present), and Latin normally follows sequence of tenses.

For a purpose clause:

• after a primary tense, Latin usually uses the present subjunctive
• after a secondary/historic tense, Latin usually uses the imperfect subjunctive

So:

• claudit ... ne terreat = present main verb + present subjunctive

If the main verb were past, you would expect something like:

• Mater fenestras clausit, ne fulgur servos et infantes terreret

No. Latin has no definite article like English the, and no indefinite article like a/an.

So:

• mater can mean mother or the mother
• fenestras can mean windows or the windows
• servos can mean slaves or the slaves

English has to choose an article when translating, but Latin usually leaves that to context.

Yes. That is often a very nice literal translation.

So:

• Mater fenestras claudit, ne fulgur servos et infantes terreat can be rendered as
• Mother closes the windows lest lightning frighten the slaves and children

In modern English, so that ... not is usually more natural, but lest is a good way to understand the Latin structure.