Cum sol oritur, milites e castris procedunt.

Here cum is a conjunction, not a preposition. As a conjunction, it means when.

So in this sentence:

Cum sol oritur = When the sun rises

Latin cum can mean different things depending on how it is used:

• cum
  • ablative noun = with
    • cum amico = with a friend
• cum introducing a clause = when, since, or although, depending on context

Here it introduces a whole clause (sol oritur), so it means when.

Sol is the subject of oritur, so it is in the nominative singular.

Its dictionary form is:

• sol, solis = sun

In the sentence:

• sol = the sun
• it is nominative because it is the thing doing the action of rising

So sol oritur literally means the sun rises.

Because oritur comes from a deponent verb.

The verb is:

• orior, oriri, ortus sum = to rise, to arise

Deponent verbs are special:

• they have passive forms
• but active meanings

So:

• oritur looks like it could mean is risen
• but it actually means rises or is rising

This is a very common thing in Latin, and learners often need time to get used to it.

Oritur is:

• 3rd person singular
• present tense
• indicative mood
• from the deponent verb orior

So it means:

• he/she/it rises
• here: the sun rises

It is singular because sol is singular.

Milites is the subject of procedunt, so it is in the nominative plural.

The noun is:

• miles, militis = soldier

Its nominative plural is:

• milites = soldiers

So milites procedunt means the soldiers advance / march forward / proceed.

Because e takes the ablative case, and castris is the ablative plural.

The noun is:

• castra, castrorum = camp

But there is an important point: castra is a plural-only noun when it means military camp. So even though English says camp in the singular, Latin uses a plural form.

Its main forms are:

• nominative/accusative plural: castra
• ablative plural: castris

Since the sentence says out of/from the camp, Latin uses:

• e castris = from the camp / out of the camp

Because Latin often uses a preposition to make the idea of movement out from a place clear.

• e or ex = out of, from

So:

• e castris = out of the camp / from the camp

Latin sometimes omits prepositions with certain place expressions, but here the normal expression is e/ex + ablative.

Both e and ex mean the same thing here: out of, from.

Usually:

• e is common before consonants
• ex is common before vowels and sometimes before certain consonants

But in practice, Latin authors can use either form depending on style and sound.

So:

• e castris
• ex castris

are both possible and both mean the same thing.

Procedunt comes from:

• procedo, procedere, processi, processum

Its basic meaning is go forward, advance, proceed, or march forward.

Here it is:

• 3rd person plural
• present indicative

So milites procedunt means:

• the soldiers advance
• the soldiers march out
• the soldiers proceed

The best English choice depends on the context, but the central idea is moving forward/out.

Because its subject, milites, is plural.

Latin verbs change form to agree with their subject:

• miles procedit = the soldier advances
• milites procedunt = the soldiers advance

So the -unt ending tells you the verb is 3rd person plural.

Classical Latin has no definite article (the) and no indefinite article (a/an) as normal separate words.

So:

• sol can mean sun or the sun
• milites can mean soldiers or the soldiers
• castris can mean camp or the camp, depending on context

English has to choose an article in translation, but Latin usually leaves that to context.

Yes. It is a subordinate temporal clause introduced by cum.

The sentence has two parts:

1. Cum sol oritur
   • When the sun rises
2. milites e castris procedunt
   • the soldiers march out from the camp

The first clause gives the time when the action in the main clause happens.

Because this is a straightforward temporal use of cum: when the sun rises.

Latin often uses:

• cum + indicative for a simple time idea
• cum + subjunctive for more literary or descriptive ideas such as when, since, or although with added nuance

Here the sentence is simple and direct, so the indicative is natural.

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

So these would still be understandable Latin:

• Milites e castris procedunt, cum sol oritur.
• Cum oritur sol, milites e castris procedunt.
• E castris milites procedunt, cum sol oritur.

However, the given order is very natural:

• first the time clause
• then the main action

Latin word order often changes for emphasis, rhythm, or style, not because the basic grammar changes.

In Latin, you usually rely more on endings than on position.

In this sentence:

• sol is nominative singular, so it is the subject of oritur
• milites is nominative plural, so it is the subject of procedunt
• castris is ablative plural after e, so it means from the camp

So even if the order changes, the endings still tell you each word’s job.

That is one of the biggest differences between Latin and English.

It can do either, depending on context.

In a sentence like this, the present tense can express a general or repeated action:

• When the sun rises, the soldiers march out from the camp.

That can sound like a regular habit or routine.

It could also be understood more vividly as present-time narration in the right context, but the most natural reading for a learner is usually the general one: whenever the sun rises, the soldiers go out.

A learner would probably want to remember these:

• cum = when (as a conjunction)
• sol, solis = sun
• orior, oriri, ortus sum = rise, arise
  
  • deponent verb
• miles, militis = soldier
• e / ex = out of, from
• castra, castrorum = camp
  
  • plural-only in the military sense
• procedo, procedere, processi, processum = go forward, advance, proceed

This sentence is useful because it combines several important beginner ideas:

• a cum clause
• a deponent verb
• case after a preposition
• a plural subject with plural verb