Lectio quarta brevis est.

All three main words are in the nominative singular:

• lectio = nominative singular
• quarta = nominative singular feminine
• brevis = nominative singular feminine
• est = is

This is because lectio is the subject, and both quarta and brevis describe that subject.

Because quarta has to agree with lectio.

Lectio is:

• feminine
• singular
• nominative

So the ordinal adjective quartus, -a, -um must also be:

• feminine
• singular
• nominative

That gives quarta.

Because brevis is a predicate adjective after est. In Latin, a predicate adjective normally matches the subject in case, number, and gender.

Since lectio is nominative singular feminine, brevis is also nominative singular feminine.

If you used brevem, that would be accusative, which would not fit here.

Lectio is a noun meaning lesson or reading, depending on context.

Its dictionary form is usually given as:

• lectio, lectionis, f.

That tells you it is:

• a third-declension noun
• feminine

In this sentence, it means lesson.

Latin has no definite article and no indefinite article. So there is no separate word for the or a/an.

That means lectio quarta brevis est can be understood as:

• The fourth lesson is short
• or, depending on context, A fourth lesson is short

Usually the context tells you which English translation sounds best.

Latin word order is much more flexible than English word order because the endings show how words relate to each other.

So Lectio quarta brevis est is natural Latin. The verb often comes near the end, especially in simple prose.

You could rearrange the words without changing the basic meaning, for example:

• Brevis est lectio quarta
• Lectio brevis est quarta

But some orders sound more natural than others depending on emphasis. The version you have is straightforward and normal.

Sometimes Latin can omit a form of to be, especially in certain styles, but in a basic sentence like this, est is normally expressed.

So for a learner, it is best to understand:

• Lectio quarta brevis est = The fourth lesson is short

and not assume that est is usually optional.

It is specifically an ordinal adjective, not a cardinal number.

• quattuor = four
• quartus, -a, -um = fourth

So quarta lectio means the fourth lesson, not four lessons.

They do two different jobs:

• quarta identifies which lesson it is: the fourth
• brevis tells you what it is like: short

So in structure:

• lectio quarta = the fourth lesson
• brevis est = is short

Together: The fourth lesson is short.

You know because of agreement.

Both lectio and quarta are:

• feminine
• singular
• nominative

In Latin, adjectives usually match the nouns they describe in gender, number, and case. That helps you connect the words, even when the word order changes.

A common classroom pronunciation is:

BREH-wis

More exactly in reconstructed classical pronunciation:

• bre- as in breh
• -vis with a w-like v sound: breh-wis

So the whole sentence could sound roughly like:

LEK-ti-o KWAR-ta BREH-wis est

Not exactly.

bonus, bona, bonum is a first-and-second-declension adjective.

But brevis, breve is a third-declension adjective.

That is why the feminine nominative singular is brevis, not something like breva.

So even though quarta and brevis both describe lectio, they belong to different adjective patterns.

It is:

• subject: lectio quarta = the fourth lesson
• linking verb: est = is
• predicate adjective: brevis = short

So the pattern is:

[subject] + [form of to be] + [adjective]

That is a very common Latin sentence pattern.