Deus per longum aevum vivit.

Because Deus is the subject of the sentence: it is the one doing the action of vivit (lives).

• Deus = God / a god
• nominative singular masculine

In Latin, the subject of a finite verb normally goes in the nominative.

Vivit is the 3rd person singular present active indicative of vivere, meaning to live.

So:

• vivo = I live
• vivis = you live
• vivit = he/she/it lives

Here it means he lives or God lives.

Per here means through, throughout, or for the duration of. With expressions of time, Latin often uses per + accusative to show that something lasts throughout a stretch of time.

So per longum aevum means something like:

• through a long age
• for a long time
• through a long era

It emphasizes duration.

Because per takes the accusative case.

So:

• aevum is accusative singular
• longum is also accusative singular because it agrees with aevum

Agreement means the adjective matches the noun in:

• case
• number
• gender

Since aevum is neuter singular accusative, the adjective must also be neuter singular accusative: longum.

Aevum means something like:

• age
• lifetime
• long period
• era

It is not just an ordinary year. It suggests a long span of time, and it can sound more elevated or literary than a very plain time word.

So per longum aevum is not just for many years in the most everyday sense; it has a broader feeling, more like through a long age or for a very long time.

The choice affects the nuance.

• annos would mean years specifically
• tempus means time more generally
• aevum suggests a long age, era, or lifetime

So per longum aevum sounds broader and more elevated than per multos annos.

Roughly:

• per multos annos vivit = he lives for many years
• per longum aevum vivit = he lives through a long age / for a very long time

Not literally. Per longum aevum means for a long time or through a long age, not necessarily forever.

If Latin wanted to express forever more directly, you might expect phrases such as:

• in aeternum
• semper
• aeternus est in some contexts, depending on the meaning intended

So this sentence suggests very long duration, but it does not automatically mean absolute eternity.

Yes, the word order is fine, and Latin word order is much freer than English word order.

This sentence is:

• Deus = subject
• per longum aevum = prepositional phrase of duration
• vivit = verb

That is a perfectly natural arrangement. But Latin could also say:

• Deus vivit per longum aevum
• Per longum aevum Deus vivit
• Vivit Deus per longum aevum

These versions keep the same basic meaning, though the emphasis can shift slightly.

Latin often places the verb near the end of the sentence, especially in simple statements. This is very common, though not required.

Putting vivit last can give the sentence a neat, complete feel:

• Deus ... vivit
• the action is revealed at the end

English usually needs a more fixed order, but Latin often uses word order for style and emphasis rather than for basic grammar.

In modern printed Latin, Deus is often capitalized when it refers to God in a monotheistic sense. But ancient Latin manuscripts did not use capitalization the same way modern editions do.

So:

• Deus in modern writing often means God
• deus can mean a god

Capitalization is mostly an editorial and modern convention, not a different grammatical form.

Yes. Depending on context, it could be rendered as:

• for a long time
• through a long age
• throughout a long era
• for a long span of time

A very literal translation may sound unnatural in English, so a smoother translation is often better. The important idea is extended duration.

Yes. It has a somewhat elevated or literary tone because of aevum. If a beginner expects a very plain sentence, this word may stand out.

A more everyday-feeling Latin sentence might use something simpler, but per longum aevum vivit sounds more grand or solemn, which fits well with Deus.