Le voyant est allumé.

Here, voyant means an indicator light, warning light, or signal light.

So Le voyant est allumé is the kind of sentence you might see for a dashboard light, a device light, or a control panel light.

A useful note: voyant can also mean psychic / clairvoyant in other contexts, but that is not the meaning here.

Because voyant is a masculine singular noun, so it takes le.

• le voyant = the indicator light
• un voyant = an indicator light

Even if an English speaker thinks of light as just light, in French you have to learn the gender of the noun. In this case, voyant is masculine.

Est is the third-person singular form of être (to be).

So:

• le voyant = the indicator light
• est = is
• allumé = lit / on

This structure is very common in French:

• Le voyant est allumé. = The indicator light is on.
• La porte est ouverte. = The door is open.
• La fenêtre est fermée. = The window is closed.

Allumé comes from the verb allumer, which means to light, to switch on, or to turn on.

So allumé literally means something like:

• lit
• switched on
• turned on

In natural English, is on is usually the best translation here.

Because voyant is masculine singular.

The form of allumé agrees with the noun it describes:

• masculine singular: allumé
• feminine singular: allumée
• masculine plural: allumés
• feminine plural: allumées

Examples:

• Le voyant est allumé.
• La lampe est allumée.
• Les voyants sont allumés.

In this sentence, it is best understood as an adjective (or adjective-like past participle) describing the state of the light.

So Le voyant est allumé means the light is in the state of being on.

French often uses être + past participle this way to describe a condition:

• La porte est fermée. = The door is closed.
• La télé est allumée. = The TV is on.

Yes, but it means something different.

• Le voyant est allumé. = The light is on.
  (state)
• Le voyant s’allume. = The light is coming on / lights up.
  (action or change)

So if you are describing the current condition, use est allumé.
If you are describing the moment it turns on, use s’allume.

It is pronounced roughly like vwah-yahn with a nasal ending.

A more careful breakdown:

• voy- sounds like vwah-y
• -ant has a nasal vowel, so the n is not fully pronounced like an English n

Approximate pronunciation:

• voyant ≈ vwah-yahn

And the whole sentence is roughly:

• Le voyant est allumé ≈ luh vwah-yahn eh tah-loo-may

That said, French pronunciation is smoother and more connected than English spelling suggests.

Not always. Its meaning depends on context.

With lights, screens, devices, candles, etc., allumé usually means:

• on
• lit

Examples:

• La lumière est allumée. = The light is on.
• L’écran est allumé. = The screen is on.

But in informal French, allumé can also have slang meanings like crazy, weird, or wild. That is a completely different use and not the one here.

French often expresses this idea differently from English.

In English, we say:

• The light is on.

In French, the common way is:

• La lumière est allumée.
• Le voyant est allumé.

So instead of using a separate word exactly like English on, French often uses allumé(e), meaning lit/switched on.

Yes. The exact English translation depends on context.

For example:

• on a machine: indicator light
• on a car dashboard: warning light
• on electronics: signal light or indicator

So Le voyant est allumé could be translated in several natural ways depending on what kind of device you are talking about.

Yes, especially in technical, everyday, or practical contexts.

You might hear or read it:

• in a manual
• on a dashboard message
• when someone is checking a device
• when talking about a machine or appliance

For example:

• Le voyant rouge est allumé. = The red warning light is on.
• Si le voyant est allumé, rechargez l’appareil. = If the indicator light is on, recharge the device.

The negative is:

Le voyant n’est pas allumé.

That means:

• The indicator light is not on.
• The warning light is not lit.

French negation is usually formed with:

• ne ... pas

So:

• est → n’est pas

Usually not in the same way.

• allumé is used for something that is lit or switched on
• en marche means running or operating

So for a light, allumé is the natural choice:

• Le voyant est allumé. = The light is on.

For a machine:

• La machine est en marche. = The machine is running.

A device can be allumé if it is switched on, but en marche focuses more on it actively operating.

Then the adjective changes to match it.

For example:

• La lampe est allumée. = The lamp is on.
• La lumière est allumée. = The light is on.

This is an important French pattern: adjectives and participles often agree in gender and number with the noun they describe.

So with voyant, you use allumé because voyant is masculine.