El desvío empieza aquí.

Because desvío is a singular masculine noun, so it normally takes the definite article el when you are talking about a specific detour.

In this sentence, el desvío means the detour. Spanish usually uses articles more often than English does, especially with nouns that refer to something specific and already identifiable from the situation, such as a road sign or a route being pointed out.

Yes, desvío is masculine: el desvío.

One clue is the ending -o, which is often masculine in Spanish, though that is not a perfect rule. In this case, the correct form is definitely el desvío.

You would also say:

• un desvío
• el desvío
• los desvíos

In this context, desvío usually means a detour or a diversion in traffic or road travel.

Depending on context, desvío can also mean:

• a deviation from a route
• a turnoff
• a diversion of traffic

In Latin America, it is very common on roads and signs. The exact English translation can vary a little by context, but for road situations detour is usually the best match.

Because the sentence needs a conjugated verb, not the infinitive.

The infinitive is empezar, meaning to begin or to start.
Here, the subject is el desvío, which is third person singular, so the verb must be conjugated:

• yo empiezo
• tú empiezas
• él/ella/usted empieza

So El desvío empieza aquí literally has the structure The detour begins here.

Also notice that empezar is a stem-changing verb: e → ie in many present-tense forms, which is why it becomes empieza, not empeza.

Yes. Comienza and empieza are both correct here.

• empezar = to start / begin
• comenzar = to begin / start

They are very close in meaning. In everyday speech, empezar is often a little more common, but comenzar sounds perfectly natural too.

So these both work:

• El desvío empieza aquí.
• El desvío comienza aquí.

Spanish often uses the simple present to state a fact, especially on signs, maps, or directions.

Here, empieza is not really talking about the future in the sense of it will start later. It is describing the current layout of the road: the detour starts here.

English does the same thing:

• The road ends here
• The tour begins here
• The speed limit changes here

So the present tense is completely natural.

The accent mark shows that the stress falls on ví: des-VÍ-o.

Without the accent, Spanish spelling rules would suggest a different stress pattern. The written accent tells you where to emphasize the word.

It also helps show that í and o are pronounced in separate syllables:

• des-ví-o → 3 syllables

That is important for pronunciation.

A simple pronunciation guide is:

• desvío ≈ dehs-VEE-oh
• aquí ≈ ah-KEE

A few notes:

• In desvío, the stress is on ví.
• In aquí, the stress is on the last syllable quí.
• The v in Spanish is usually pronounced much closer to b than to the English v.
• The qu in aquí sounds like a hard k.

So the full sentence sounds roughly like:

el dehs-BEE-oh em-PYEH-sah ah-KEE

That is only an approximation, but it is useful for an English speaker.

Often, yes. In many Latin American varieties, aquí and acá can both mean here, but they are not always used in exactly the same way.

In this sentence, both are possible:

• El desvío empieza aquí.
• El desvío empieza acá.

Very generally:

• aquí can sound a bit more precise: right here
• acá can sound a bit more general or more natural in some regions

That said, usage depends a lot on the country and even the speaker. Aquí is safe and standard everywhere.

Yes. Aquí empieza el desvío is also correct.

Spanish allows more flexibility in word order than English. The original sentence:

• El desvío empieza aquí

is a neutral statement.
If you say:

• Aquí empieza el desvío

you place more focus on aquí, as if pointing out the location.

Both versions are natural.

Yes, and that can confuse learners.

Desvío can be:

1. a noun meaning detour or deviation
2. a verb form of desviar: yo desvío = I divert / I deviate / I reroute

For example:

• El desvío empieza aquí. → here desvío is a noun
• Yo desvío el tráfico. → here desvío is a verb

You can tell which one it is from the context and sentence structure.

Yes, it sounds natural and clear.

As a full sentence, El desvío empieza aquí is perfectly normal for spoken Spanish or for an informational sign. On actual road signs, though, Spanish is often more compressed, so you might also see shorter wording such as:

• Desvío
• Inicio de desvío
• Desvío aquí

But as a complete sentence for learners, El desvío empieza aquí is very natural.