Auriga habena longa utitur, dum equa caput movet et iuba ventis agitatur.

A helpful first step is to find the finite verbs:

• utitur = uses
• movet = moves
• agitatur = is driven / is tossed / is stirred

Then match each verb with its subject:

• Auriga ... utitur = the charioteer uses ...
• equa caput movet = the mare moves her head
• iuba ventis agitatur = the mane is tossed by the winds

And dum links the actions by meaning while:

• Auriga habena longa utitur, dum equa caput movet et iuba ventis agitatur.

So the sentence is basically:

• main clause: Auriga ... utitur
• subordinate clause with dum: equa caput movet et iuba ventis agitatur

Because auriga is one of those Latin nouns that belongs to the first declension in form but is masculine in meaning and grammar.

This often happens with nouns for male professions or roles, for example:

• nauta = sailor
• agricola = farmer
• poeta = poet
• auriga = charioteer

So even though auriga looks like a typical first-declension feminine noun, here it is masculine.

Because utor, uti, usus sum is a deponent verb.

A deponent verb:

• has passive forms
• but an active meaning

So:

• utitur is grammatically a passive-looking form
• but it means he/she uses, not he/she is used

Specifically, utitur is:

• 3rd person singular
• present tense
• indicative
• from utor

So Auriga ... utitur means The charioteer uses ...

Because utor takes the ablative case for the thing used.

So instead of using an accusative direct object, Latin says:

• habena utitur = he uses a rein
• literally, something like he makes use of a rein

That is why:

• habena is ablative singular
• longa is also ablative singular, agreeing with habena

Agreement matters:

• habena = feminine, singular, ablative
• longa = feminine, singular, ablative

So habena longa means with a long rein / a long rein after utitur.

Yes, English often prefers reins in the plural, but Latin can use the singular naturally here.

Possible reasons:

• it may refer to one rein/strap
• it may describe the instrument more generally
• Latin and English do not always use singular and plural in exactly the same way

So habena longa is perfectly normal Latin, even if an English translation might sometimes choose long reins for natural style.

Here dum means while.

It introduces an action happening at the same time as the action in the main clause:

• Auriga ... utitur = the charioteer uses ...
• dum equa caput movet ... = while the mare moves her head ...

So dum is marking simultaneous action.

Because with dum meaning while, Latin very commonly uses the present indicative to describe an action going on at the same time.

So:

• dum equa caput movet = while the mare moves her head

Even if English might sometimes vary its tense depending on context, the Latin present here is completely standard.

movet is:

• 3rd person singular
• present indicative active
• from moveo, movere

Because caput is a neuter noun, and in Latin many neuter nouns have the same form in the nominative and accusative singular.

So:

• caput can be nominative singular
• caput can also be accusative singular

Here it is the direct object of movet:

• equa caput movet = the mare moves her head

You can tell from the syntax:

• equa is the subject
• movet is the verb
• caput is what is being moved

Agitatur is:

• 3rd person singular
• present indicative passive
• from agito, agitare

It means something like:

• is driven
• is stirred
• is tossed

In this sentence, the subject is iuba:

• iuba ventis agitatur = the mane is tossed by the winds

So unlike utitur, which is a deponent verb with active meaning, agitatur is a true passive.

We know from the sentence structure.

In iuba ventis agitatur:

• agitatur is singular, so it needs a singular subject
• iuba fits naturally as that subject
• ventis is ablative plural, so it works better as by the winds or with the winds, not as the subject

So the phrase means:

• the mane is tossed by the winds

Without macrons, iuba could in theory look like either nominative or ablative singular in form, but the grammar of the sentence makes the nominative reading the right one here.

Ventis is the ablative plural of ventus, meaning wind.

Here it expresses the force or means causing the action:

• iuba ventis agitatur = the mane is tossed by the winds

Latin often uses the ablative without a preposition for things like means, instrument, or impersonal force.

So with an inanimate thing like winds, Latin does not need ab.

A useful contrast:

• ab homine = by a person
• vento / ventis = by the wind / by the winds

Because Latin word order is much freer than English word order. Latin relies more on case endings and verb forms than on position.

English usually needs a fixed order like:

• subject + verb + object

Latin can move words around for emphasis, rhythm, or style.

In this sentence:

• Auriga comes first to set the scene
• habena longa stays together because the noun and adjective belong closely together
• ventis comes before agitatur to highlight what is causing the mane to move

So the order is not random, but it is also not locked into English patterns.

Yes. In Latin, an adjective normally agrees with the noun it describes in:

• gender
• number
• case

Here:

• habena = feminine, singular, ablative
• longa = feminine, singular, ablative

So longa matches habena exactly.

This agreement is one of the main clues that the two words belong together as a phrase: habena longa.