El torno gira despacio.

Because gira is the conjugated form of the verb, while girar is the infinitive.

• girar = to turn / to spin
• gira = turns / is turning

In this sentence, the subject is el torno, so the verb has to match he/she/it form in the present tense:

• yo giro = I turn
• tú giras = you turn
• él/ella gira = he/she turns
• el torno gira = the lathe / wheel / turnstile turns

So gira is the correct form here.

Spanish often leaves out subject pronouns when they are clear from the verb or from the noun already stated.

In English, you must say It turns slowly.
In Spanish, if you already say El torno, you do not need an extra it:

• El torno gira despacio.

You would not normally say something like El torno él gira despacio. That sounds wrong in Spanish.

Spanish is a pro-drop language, which means subject pronouns are often omitted.

Because in Spanish, adverbs like despacio often come after the verb.

So:

• gira despacio = turns slowly

This is the most natural word order here.

Spanish word order is often more flexible than English, but verb + adverb is very common.
Putting despacio elsewhere is possible in some contexts, but it may sound more marked or literary:

• El torno gira despacio. = normal
• Despacio gira el torno. = unusual, poetic, or for emphasis

For a learner, the safest pattern is:

subject + verb + adverb

Here, despacio is an adverb because it describes how the turning happens.

It answers the question:

• How does it turn?
• Despacio = slowly

Adverbs do not change for gender or number, so despacio stays the same:

• El torno gira despacio.
• La rueda gira despacio.
• Los tornos giran despacio.

It does not become despacia or despacios.

Yes. Torno is a masculine noun, so it takes el in the singular:

• el torno
• los tornos

In Spanish, every noun has grammatical gender, and the article must match it.

So:

• el = masculine singular
• la = feminine singular

Even if the object has no biological sex, the noun still has grammatical gender.

Yes. In many contexts, the Spanish present tense can translate as either:

• turns
• is turning

So El torno gira despacio could mean:

• The lathe turns slowly
• The lathe is turning slowly

Spanish often uses the simple present where English might use either the simple present or the present continuous, depending on context.

If you wanted to make the ongoing action especially clear, Spanish could also say:

• El torno está girando despacio.

But the original sentence is completely normal.

Yes, you could say:

• El torno gira lentamente.

Both despacio and lentamente can mean slowly, but there is a slight difference in feel:

• despacio = very common, everyday, natural
• lentamente = a bit more formal or descriptive

In ordinary speech, despacio is often the more common choice.

In Spain, gira is pronounced roughly like:

• HEE-rah, but with a stronger, raspier h sound

More precisely:

• gi before i gives a throaty sound, like the Spanish j
• the r in gira is a single tap, not a strong rolled rr

So gira is approximately [ˈxiɾa] in standard Spain Spanish.

A native English speaker should especially notice that:

• g before i is not a hard English g
• the r is quick and light

In Spain, torno is roughly:

• TOR-noh

A few useful points:

• t is a clean dental t
• o is a pure vowel, not a diphthong like English oh
• r here is a single tap
• stress falls on the first syllable: TOR-no

So the stress is:

• TOR-no

Normally, no. In this sentence, you need the article:

• El torno gira despacio.

Spanish often uses articles where English might or might not use them. Here, torno is a normal countable noun used as the subject, so leaving out el would usually sound incorrect.

You would only omit the article in very different structures, not in this simple sentence.

Spanish word order is more flexible than English, but that does not mean all orders are equally natural.

The most neutral version is:

• El torno gira despacio.

Other orders may be possible for emphasis, style, or poetry, but they are not the basic learner pattern.

For example:

• Despacio gira el torno. = possible, but marked
• Gira despacio el torno. = possible in some contexts, but less neutral

If you are learning, the safest and most natural version is the original one.

Because despacio is not describing the noun torno. It is describing the action gira.

Compare:

• El torno lento = the slow lathe
  Here lento is an adjective describing the noun, so it agrees with the noun.
• El torno gira despacio = the lathe turns slowly
  Here despacio is an adverb describing the verb, so it does not agree.

That is why despacio stays unchanged.

The structure is:

article + noun + verb + adverb

So:

• El = the
• torno = noun
• gira = verb
• despacio = adverb

This is a very common and useful Spanish sentence pattern. It is a good model for making similar sentences, for example:

• La rueda gira rápido.
• El ventilador funciona bien.
• La máquina avanza lentamente.