O visor está apagado.

Not usually. In Portuguese, visor often means a display, screen, or viewfinder, depending on the device.

So in O visor está apagado, visor most naturally means something like a display/screen.

It is only sometimes the same as English visor (like the part of a helmet or cap), depending on context.

O is the masculine singular definite article, meaning the.

• o visor = the display / the screen

Portuguese uses definite articles very naturally in places where English may or may not use the. In a normal full sentence, O visor sounds natural and complete.

Because está comes from estar, which is used for states or conditions.

Here, apagado describes the current condition of the display: it is off / dark / not lit.

So:

• está apagado = is off / is dark

Using ser (é) would sound wrong here, because the sentence is not describing what the display is, but what state it is in.

Here, apagado means off, unlit, or dark.

It comes from the verb apagar, which can mean things like:

• to turn off
• to extinguish
• to erase

With lights and screens, apagado usually means that the light/display is not on.

So for a screen:

• está apagado = it’s off / the screen is dark

Because apagado is agreeing with visor, which is a masculine singular noun.

In Portuguese, adjectives usually agree with the noun they describe.

Here are the forms:

• o visor está apagado — masculine singular
• a luz está apagada — feminine singular
• os visores estão apagados — masculine plural
• as luzes estão apagadas — feminine plural

Está is the 3rd person singular present indicative of estar.

So:

• eu estou — I am
• tu estás — you are
• ele/ela/você está — he/she/you is/are

In this sentence, o visor is treated like it, so Portuguese uses está.

Normally, no.

O visor está apagado is the natural sentence for The display is off.

É apagado would usually suggest something more like a general characteristic or a passive meaning in another context, and it does not sound right for a device’s current on/off state.

For temporary conditions like this, use estar:

• está apagado

Sometimes, but the meaning shifts a bit.

• apagado focuses on the fact that the screen/display is dark / not lit
• desligado focuses more on something being switched off / powered off

So:

• A screen is very naturally apagado
• A whole device is very naturally desligado

For example:

• O visor está apagado. = The display is off/dark.
• O telemóvel está desligado. = The phone is switched off.

In some contexts both may be possible, but apagado is especially natural for lights and screens.

In form, it is the past participle of apagar, but in this sentence it is functioning like an adjective after estar.

This is very common in Portuguese:

• A porta está fechada. — The door is closed.
• A luz está acesa. — The light is on.
• O visor está apagado. — The display is off.

So although it comes from a verb, here it describes a state.

In a normal sentence, that sounds incomplete or unnatural.

The standard version is:

• O visor está apagado.

You might see the article omitted in very short technical notes, labels, or certain special contexts, but for ordinary speech and writing, keep o.

The normal order is:

• O visor = subject
• está = verb
• apagado = adjective/state

So the structure is:

subject + estar + adjective

This is the most neutral and natural order.

A careful pronunciation is roughly:

oo vee-ZOR esh-TA ah-pah-GAH-doo

A more IPA-style version is approximately:

[u viˈzoɾ ɨʃˈta ɐpɐˈɣaðu]

A few useful notes for European Portuguese:

• está often sounds more like shtá than a clear es-tá
• unstressed vowels are often reduced
• the final -o often sounds like a weak u

So in real speech, it may sound more compressed than you expect from the spelling.

Mostly, yes, in modern everyday usage.

Visor is commonly used for:

• a device display
• a digital readout
• a camera viewfinder
• similar visual display areas

So O visor está apagado is very natural when talking about something with a screen or display that is not lit.