Cum omen non clarum esset, augur tamen dixit navem e portu exire posse.

In this sentence, cum introduces a subordinate clause giving the background or circumstances for the main action:

Cum omen non clarum esset = since / when the omen was not clear

Latin very often uses cum with the subjunctive when the clause is not just a simple time-marker, but gives context, cause, or background. This is commonly called a cum circumstantial or cum causal clause.

So esset is subjunctive because the clause is presenting the situation in which the augur spoke.

Both come from esse, meaning to be, but they are different moods:

• erat = imperfect indicative
• esset = imperfect subjunctive

Latin chooses esset here because the clause with cum calls for the subjunctive. If the sentence had used erat, it would sound more like a straightforward factual statement of time, not the same kind of backgrounded circumstance.

So the difference is not mainly tense, but mood:

• erat = plain statement
• esset = subordinate background clause after cum

It is the subject and predicate expression of esset.

• omen = subject, the omen
• non clarum = predicate adjective, not clear

So literally:

• omen = the omen
• non clarum esset = was not clear

Because omen is neuter singular, the adjective clarum is also neuter singular to agree with it.

Because it agrees with omen, which is a neuter noun.

Latin adjectives must agree with the nouns they describe in:

• gender
• number
• case

Here:

• omen is neuter singular nominative
• so clarum must also be neuter singular nominative

That is why it is clarum, not clarus or clara.

Tamen means nevertheless, still, or however.

It marks a contrast:

• the omen was not clear
• nevertheless the augur said the ship could leave

So it highlights that the augur’s statement came despite the unclear omen.

Augur is a noun meaning a Roman religious official who interpreted signs, especially omens. Grammatically here it is:

• nominative singular
• the subject of dixit

So augur dixit means the augur said.

Because Latin uses the accusative + infinitive construction for indirect statement after verbs like dixit.

In English we say:

• he said that the ship could leave

In Latin, instead of a that-clause, you usually get:

• dixit navem ... posse

Here:

• navem = accusative subject of the infinitives
• exire posse = to be able to leave

So navem is not the direct object in the ordinary sense; it is the subject of the indirect statement, and in Latin that subject goes into the accusative.

Because that is the normal Latin pattern for indirect statement.

After verbs of saying, thinking, knowing, hearing, and so on, Latin usually uses:

• accusative subject
• plus infinitive verb

So:

• dixit navem e portu exire posse

literally looks like:

• he said the ship to be able to go out from the harbor

but naturally means:

• he said that the ship could leave the harbor

This construction is one of the most important features of Latin syntax.

Because posse means to be able, and it regularly takes another infinitive to complete its meaning.

So:

• exire = to go out, to leave
• posse = to be able

Together:

• exire posse = to be able to leave

In the indirect statement after dixit, the whole idea is:

• navem e portu exire posse = that the ship could leave the harbor

Because this is an indirect statement after dixit.

In Latin indirect statement, the verb is normally put in the infinitive, not in a finite tense like exit, exibat, or exivit.

So:

• navem ... exire posse = that the ship could leave

If Latin used a finite verb here, it would not be the normal indirect statement construction.

E or ex means out of or from and takes the ablative case.

Here:

• portu is ablative singular of portus
• so e portu = out of the harbor / from the harbor

Latin uses both e and ex before words, with the choice often depending on sound and style. Both mean the same thing here.

Because the preposition e / ex always takes the ablative.

So:

• e portu = from the harbor
• portu is ablative singular because the preposition requires it

This is a very common Latin pattern:

• in urbe = in the city
• cum amico = with a friend
• e portu = out of the harbor

Because navem is the accusative subject of the indirect statement, and that subject logically goes with exire posse.

So the structure is:

• dixit
• navem = subject of the reported statement
• exire posse = to be able to leave

Therefore it means:

• he said that the ship could leave

not:

• he said that someone could leave the ship

The accusative noun tells you who or what performs the infinitive action.

Latin word order is much more flexible because endings show grammatical relationships.

In this sentence:

• Cum omen non clarum esset
• augur tamen dixit
• navem e portu exire posse

the order helps with emphasis and style more than basic grammar. For example:

• cum clause first gives the background
• tamen is placed prominently to stress contrast
• posse comes at the end, which is very natural in Latin

English depends more on fixed word order. Latin depends more on case endings and verb forms.

Since posse is a present infinitive, it usually shows action that is contemporaneous with the main verb of saying.

So dixit navem exire posse means roughly:

• he said that the ship could leave
• or he said that the ship was able to leave

The idea is that, at the time he spoke, the ship had the ability or permission to depart.

If Latin had wanted to show earlier or later time more clearly, it could use different infinitive forms or other wording.

Grammatically, it can suggest either when or since, depending on context.

Because the clause gives background and also sounds somewhat causal, English might translate it as:

• when the omen was not clear
• or since the omen was not clear

The important point for a learner is that this cum + subjunctive clause is not just a simple clock-time expression. It gives the circumstances under which the augur made his statement.