A roda de oleiro está no centro.

A is the definite article, so a roda means the wheel.

Use a when you mean a specific wheel or one already known from the context.
Use uma when you mean a wheel, not a particular one.

So:

• A roda de oleiro está no centro. = The potter’s wheel is in the center.
• Uma roda de oleiro está no centro. = A potter’s wheel is in the center.

Because roda is a feminine noun in Portuguese. Nouns have grammatical gender, and roda takes feminine articles and adjectives:

• a roda
• esta roda
• a roda grande

This is grammatical gender, not biological gender. A wheel is not female; the noun is simply treated as feminine in the language.

Here de oleiro works like a classifying phrase: it tells you what kind of wheel it is.

So roda de oleiro means potter’s wheel in the same way that Portuguese often uses noun + de + noun:

• máquina de lavar = washing machine
• copo de vinho = wine glass
• roda de oleiro = potter’s wheel

This is very natural in Portuguese and often corresponds to English compounds or possessive-style phrases.

Because de oleiro usually names the type of object, while do oleiro usually suggests possession or association with a specific potter.

Compare:

• roda de oleiro = potter’s wheel, the type of wheel used by potters
• a roda do oleiro = the potter’s wheel, meaning the wheel belonging to a particular potter

So in your sentence, de oleiro is the normal dictionary-style expression for the object itself.

Portuguese usually uses estar for location:

• A roda de oleiro está no centro.

That is because the sentence is saying where something is.

A quick rule:

• ser = identity, classification, permanent-type description
• estar = location, state, condition

Examples:

• É uma roda de oleiro. = It is a potter’s wheel.
• Está no centro. = It is in the center.

So está is the correct choice here.

No is a contraction of:

• em
  • o = no

So:

• no centro = in the center

This kind of contraction is very common in Portuguese:

• em + a = na
• em + os = nos
• em + as = nas

Examples:

• no centro
• na sala
• nos livros
• nas caixas

You normally do not say em o centro in standard Portuguese; you contract it to no centro.

Because centro is a masculine noun:

• o centro

So:

• em + o centro → no centro

If the noun were feminine, you would use na:

• na casa
• na roda

Since centro is masculine, no centro is correct.

Yes. The normal neutral order is:

• A roda de oleiro está no centro.

But Portuguese can change the order for emphasis or style:

• No centro está a roda de oleiro.

That version is more marked and can sound more literary or emphatic, as if you are highlighting the location first.

For most learners, the original order is the safest and most natural one to use in everyday speech.

Because in roda de oleiro, oleiro is part of a fixed descriptive phrase, not a specific person being identified.

If you said:

• a roda do oleiro

then you would be referring to the potter as a specific person.

But in:

• roda de oleiro

you are just naming the kind of wheel. That is why there is no article before oleiro.

Only if you specifically want to refer to a female potter in a non-fixed, more literal way. But as the usual name of the object, roda de oleiro is the standard expression.

So:

• roda de oleiro = the normal term potter’s wheel

Even though oleira exists for female potter, the established name of the tool is typically roda de oleiro.

A careful approximation is:

a RÔ-da d’ul-AY-ru es-TA nu SEN-tru

A few useful notes for European Portuguese:

• Unstressed vowels are often reduced.
• de oleiro often sounds close to d’oleiro in connected speech.
• está has stress on the second syllable: es-TÁ
• centro is stressed on the first syllable: CEN-tro

If you already know some Brazilian Portuguese, European Portuguese may sound more compressed because many unstressed vowels are weaker or less clearly pronounced.