Milites lente procedunt, quia via angusta est.

Milites means soldiers. Here it is nominative plural, because it is the subject of procedunt.

A learner may notice that milites can also be accusative plural in other contexts, but here the verb procedunt means they advance / they proceed, so milites is naturally understood as the subject: the soldiers.

Because lente is an adverb, while lenta would be an adjective.

• lentus, lenta, lentum = slow
• lente = slowly

Since the sentence is describing how the soldiers advance, Latin uses the adverb lente: The soldiers advance slowly.

Procedunt is:

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

It comes from procedo, procedere, meaning to go forward, advance, or proceed.

So procedunt means they advance or they proceed.

Latin has no definite article like English the, and no indefinite article like a/an either.

So:

• milites can mean soldiers or the soldiers
• via can mean road or the road

You understand the exact sense from the context.

Quia means because. It introduces a reason or cause.

So the sentence is divided like this:

• Milites lente procedunt = The soldiers advance slowly
• quia via angusta est = because the road is narrow

Because angusta must agree with via.

• via is feminine
• singular
• nominative

So the adjective must also be:

• feminine
• singular
• nominative

That gives angusta.

If it were angustus, it would be masculine singular, which would not match via.

Because est belongs only to the second clause:

• Milites lente procedunt = main clause
• quia via angusta est = subordinate clause

In that second clause, the subject is via (the road), which is singular, so the verb must also be singular: est = is.

Not as much as in English. Latin uses endings more than word order to show grammatical function.

So Milites lente procedunt, quia via angusta est is a normal, clear order, but Latin could rearrange parts of it for emphasis, for example:

• Lente milites procedunt
• Quia angusta via est, milites lente procedunt

The basic meaning would stay the same, though some orders sound more natural than others.

In Latin, adjectives can come before or after the noun. Both are possible.

So:

• via angusta
• angusta via

both mean narrow road.

In many simple textbook sentences, you often see the adjective after the noun, but Latin is flexible.

Yes. Latin often leaves out the subject pronoun or even the subject noun if it is already clear from the verb.

Since procedunt already means they advance, Latin could simply say:

• Lente procedunt, quia via angusta est.

That would mean They advance slowly because the road is narrow.

Adding milites makes the subject explicit: the soldiers.

Via is nominative singular.

It is the subject of est in the clause via angusta est.

Its dictionary form is via, viae, a first-declension feminine noun, meaning road or way.

In a straightforward sentence like this, quia is followed by the indicative, because the reason is presented as a fact:

• quia via angusta est = because the road is narrow

That is why you see est, the present indicative of sum.

In elementary Latin, you can usually think of quia as introducing a normal factual because clause.