Servus grave onus subit.

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

Also, the verb subit is 3rd person singular, so it matches a singular subject such as servus.

A useful contrast is this:

• servus = nominative singular
• servum = accusative singular

Since the sentence has servus, not servum, it is understood as the subject.

Because -us does not always mean a 2nd-declension masculine noun.

Onus is a 3rd-declension neuter noun. Its forms are different from a noun like servus.

So:

• servus is 2nd declension, masculine
• onus is 3rd declension, neuter

This is a very common beginner trap: seeing -us and assuming it must be masculine nominative singular. In Latin, you have to know the declension and the dictionary form, not just the ending by itself.

Here onus is the direct object, so it is functioning as an accusative singular.

The reason this can look confusing is that neuter nouns have the same form in the nominative and accusative. So for onus, the nominative singular and accusative singular are both onus.

That means the form itself could be either nominative or accusative, but in this sentence its job is accusative because it is the thing being borne or undergone.

Because the adjective has to agree with onus in gender, number, and case.

Onus is:

• neuter
• singular
• accusative in this sentence

So the adjective must also be neuter singular accusative, which is grave.

Compare:

• gravis = masculine/feminine nominative singular
• gravem = masculine/feminine accusative singular
• grave = neuter nominative or accusative singular

Since onus is neuter, grave is the correct form.

Subit is:

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

So it means he/she/it goes under, or in this context more naturally he/she/it undergoes, takes on, or bears.

With servus as the subject, it means the slave/servant bears or undergoes the burden.

Yes. Subit comes from subeo, subire, which is a compound of:

• sub- = under
• eo = I go

So literally the verb has the idea of going under. From that literal sense, it can also mean things like:

• undergo
• submit to
• take on
• bear

Latin compound verbs often keep the character of the simple verb, even when the meaning becomes more figurative.

Because Latin often uses physical imagery in a more abstract way.

A person who goes under a burden is, in effect, taking it upon himself or bearing it. So the literal idea develops into an idiomatic one.

That is why grave onus subire can mean not only something physically like go under a heavy load, but also more generally take on a heavy burden or undergo a serious burden.

Yes, the words could be arranged differently.

Latin word order is much freer than English word order because the endings help show what each word is doing. The order here is perfectly normal, especially with the verb at the end, which is very common in Latin.

For example, Latin could also say:

• grave onus servus subit
• servus subit grave onus
• onus grave servus subit

These do not all sound exactly the same in emphasis, but they can express the same basic idea. Word order in Latin often helps with focus or style, not just grammar.

There is no word for the or a because Classical Latin does not have articles like English does.

So servus can mean:

• a slave
• the slave
• sometimes a servant or the servant, depending on context

And grave onus can mean:

• a heavy burden
• the heavy burden
• a serious burden
• the serious burden

You decide from context which English article sounds best.

In Classical Latin, servus most often means slave.

In some teaching materials it is sometimes translated more gently as servant, especially at a beginner level, but slave is usually the more historically accurate core meaning.

So if you are reading real Roman texts, it is good to remember that servus usually refers to an enslaved person, not just a hired worker.

It can mean either, depending on context.

Gravis, grave has a range of meanings, including:

• heavy
• weighty
• serious
• severe
• burdensome

So grave onus could be a literally heavy load, but it could also be a difficult responsibility or hardship. Latin often allows both a concrete and a figurative sense at the same time.

Because grave is an adjective agreeing with onus.

They match in:

• gender: neuter
• number: singular
• case: accusative here

That agreement tells you that grave describes onus. So you should read them together as one noun phrase: a heavy/serious burden.

This is one of the main ways Latin shows which words belong together, even when word order is flexible.