Sit haec lectio brevis, sed nullum vocabulum neglegatur.

Because this sentence is giving a kind of wish, exhortation, or command, not just stating a fact.

Latin often uses the present subjunctive for this, especially in the third person:

• sit = let it be / may it be
• neglegatur = let it be neglected / in context with nullum, let no word be neglected

This is called the jussive subjunctive. English usually translates it with let ... or sometimes may ....

So:

• haec lectio brevis est = this lesson is brief
• sit haec lectio brevis = let this lesson be brief

Haec means this and is a demonstrative adjective here.

It agrees with lectio in:

• gender: feminine
• number: singular
• case: nominative

So haec lectio means this lesson.

Because lectio is feminine singular nominative, the correct form is haec.

Because lectio, lectionis is simply a feminine noun in Latin. Nouns in Latin have grammatical gender, and that gender is something you learn with the word.

So when you use adjectives or demonstratives with lectio, they must also be feminine:

• haec lectio
• lectio brevis

Even though lesson is not feminine in English, Latin grammar requires agreement with the noun’s grammatical gender.

Because brevis is agreeing with lectio.

Here brevis is a predicate adjective, describing the subject lectio after sit. Since lectio is:

• feminine
• singular
• nominative

the adjective must also be feminine singular nominative.

For the adjective brevis, breve:

• masculine nominative singular: brevis
• feminine nominative singular: brevis
• neuter nominative singular: breve

So brevis is correct because it matches lectio.

Because vocabulum is a neuter singular noun, and nullum must agree with it.

• vocabulum = word, vocabulary item
• nullum = no, not any

In this sentence, vocabulum is the thing being neglected, so it is the direct object of the verb. That means it is in the accusative case.

Since vocabulum is neuter singular accusative, the adjective must also be neuter singular accusative:

• nullum vocabulum = no word

This is a very good question, because it can look surprising at first.

The important point is that nullum vocabulum is the subject in sense of the passive idea, but in form, Latin allows this construction because neglegatur is a passive jussive with the noun understood as the thing affected.

However, many learners will first expect a nominative like nullum vocabulum to be subject—but in fact, for vocabulum, the nominative and accusative singular are identical.

So the form vocabulum could be either nominative or accusative just by shape alone.

Here the better way to understand it is:

• nullum vocabulum is effectively neuter singular nominative
• nominative and accusative neuter singular look the same

That is why the form is nullum vocabulum. With a neuter second-declension noun, nominative singular and accusative singular are both -um.

In this sentence, it is best understood as nominative, because neglegatur is passive: let no word be neglected.

The confusion happens because with neuter nouns:

• nominative singular = accusative singular

So:

• nominative: vocabulum
• accusative: vocabulum

And likewise:

• nominative neuter singular of nullus: nullum
• accusative neuter singular: nullum

So the form does not change, even though the syntactic role does.

Because the sentence wants to focus on the word rather than on the person who might neglect it.

Latin could have said something active, such as:

• sed nemo ullum vocabulum neglegat
  = but let no one neglect any word

But the actual sentence says:

• sed nullum vocabulum neglegatur
  = but let no word be neglected

That sounds a little more formal and impersonal, and it keeps attention on every word.

Neglegatur is:

• present
• subjunctive
• passive
• third person singular

It comes from neglego, neglegere, neglexi, neglectum = to neglect.

The ending -atur is the normal ending for a third-person singular present passive subjunctive in the third conjugation.

So:

• neglegit = he/she/it neglects
• neglegitur = he/she/it is neglected
• neglegatur = let it be neglected / may it be neglected

With nullum vocabulum, it means let no word be neglected.

Sit is the present subjunctive, third person singular, of sum, esse (to be).

Compare:

• est = it is
• sit = let it be / may it be

Since lectio is singular, the verb is singular too.

Yes. Sed is a very common coordinating conjunction meaning but.

It connects the two balanced parts of the sentence:

• Sit haec lectio brevis
• sed nullum vocabulum neglegatur

So the sentence has a neat contrast:

• let the lesson be brief
• but let no word be neglected

Yes, Latin word order is much freer than English word order.

This sentence is arranged for style and emphasis:

• Sit haec lectio brevis puts the verb first, which gives a formal, almost motto-like tone.
• nullum vocabulum comes before neglegatur, emphasizing no word.

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

• Haec lectio brevis sit
• Sed vocabulum nullum neglegatur

But the original order sounds polished and deliberate.

Yes. Both are natural ways to translate the jussive subjunctive.

For example:

• Sit haec lectio brevis = May this lesson be brief
• sed nullum vocabulum neglegatur = but may no word be neglected

Or more idiomatically in English:

• Let this lesson be brief, but let no word be neglected.

Usually let sounds a little more natural in English for this kind of sentence.

In many learning contexts, vocabulum often means a word as a vocabulary item, not just a random spoken utterance.

So in this sentence it strongly suggests:

• no vocabulary item
• not a single word in the lesson

That is why the sentence fits well in a teaching context.

Yes. It is short, balanced, and elegant.

The sentence has two matching jussive subjunctives:

• sit
• neglegatur

And it sets up a contrast:

• brevis = brief
• nullum vocabulum neglegatur = but still thorough

So the style is compact and memorable, almost like a classroom principle:

Let the lesson be short, but let no word be overlooked.