Labrum pueri adhuc rubet.

Because rubet is a singular verb, and labrum is in the nominative singular, which is the normal case for the subject.

Here, labrum is a second-declension neuter noun:

• nominative singular: labrum
• accusative singular: labrum

So the form could in theory be either nominative or accusative, but the sentence structure shows it is the subject: the lip is what is red.

Because pueri can be more than one thing:

• genitive singular = of the boy
• nominative plural = the boys

In this sentence, pueri is understood as genitive singular because it shows possession: the boy’s lip.

If pueri were the subject meaning the boys, the sentence would be harder to make sense of, since labrum would then be left hanging awkwardly. Also, the verb rubet is singular, not plural. If the boys were the subject, you would expect rubent.

Pueri is in the genitive singular. The genitive often shows possession or close connection.

So:

• labrum pueri = the boy’s lip or the lip of the boy

This is a very common Latin pattern:

• liber pueri = the boy’s book
• equus puellae = the girl’s horse

Because rubet is a verb, from rubeō, meaning to be red or sometimes to grow red.

English often uses:

• a linking verb + adjective: is red

Latin can do that too:

• labrum pueri rubrum est

But Latin also very naturally uses a verb like rubet:

• labrum pueri rubet = the boy’s lip is red

So this is not missing a word like est. The redness is already built into the verb rubet.

Yes. That would also be good Latin.

There is a small difference in structure:

• rubet = is red using a verb
• rubrum est = is red using an adjective plus est

Both are possible. The version with rubet is a little more compact and vivid.

Adhuc is an adverb. Here it means still.

It modifies the verb rubet:

• adhuc rubet = is still red

Common meanings of adhuc include:

• still
• up to this point
• yet in some contexts

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

This sentence could be rearranged in several ways without changing the basic meaning, for example:

• Pueri labrum adhuc rubet
• Adhuc labrum pueri rubet
• Labrum adhuc pueri rubet

However, not all orders sound equally natural in every context. The given order is perfectly normal and clear:

• labrum pueri stays together as a noun phrase
• adhuc sits near the verb it modifies
• rubet comes at the end, which is very common in Latin

Because Classical Latin has no definite article and no indefinite article.

So Latin does not normally have separate words for:

• the
• a
• an

Whether you translate labrum as the lip or a lip depends on context. In this sentence, English naturally uses the boy’s lip.

The ending -et tells you it is third person singular present active.

From rubeō:

• rubeō = I am red
• rubēs = you are red
• rubet = he/she/it is red
• rubent = they are red

So rubet matches a singular subject, which fits labrum.

Yes. Labrum is neuter, second declension.

That matters because neuter nouns have some special patterns:

• nominative singular often ends in -um
• accusative singular is the same as nominative singular
• nominative plural and accusative plural often end in -a

In this sentence, the neuter gender does not change the translation much, but it helps you recognize the form.

You would need both the noun and the verb to become plural:

• Labra pueri adhuc rubent

Breakdown:

• labra = lips, nominative plural neuter
• pueri = of the boy, genitive singular
• rubent = are red, third person plural

So singular labrum ... rubet becomes plural labra ... rubent.