La porte arrière de la maison est fermée.

In French, most descriptive adjectives come after the noun, so porte arrière is the normal order.

• porte = door
• arrière = rear / back

So literally it is something like door rear, which French uses where English says back door.

A few common adjectives do come before the noun, but arrière in this meaning normally comes after.

Here, arrière means rear or back.

So la porte arrière means the back door or the rear door.

Be careful: arrière can also appear in other contexts with slightly different meanings, such as:

• à l’arrière = at the back
• en arrière = backward / behind
• l’arrière = the rear

But in this sentence, it is simply an adjective describing which door it is.

de la maison means of the house.

French often uses de to link two nouns, where English might use of or just place one noun before another.

So:

• la porte arrière de la maison = the back door of the house

This tells us which back door we are talking about: the one belonging to the house.

Because maison is a feminine singular noun, and it needs the definite article la.

So:

• de + la maison = of the house

French usually keeps the article in this structure:

• la fenêtre de la voiture = the window of the car
• la cuisine de la maison = the kitchen of the house

You do sometimes see de without an article, but not in a sentence like this.

Because porte is feminine singular, and fermée agrees with it.

• fermé = masculine singular
• fermée = feminine singular
• fermés = masculine plural
• fermées = feminine plural

Since la porte is feminine singular, French writes:

• La porte ... est fermée.

This agreement is very common with adjectives and past participles used like adjectives.

It is a past participle of fermer (to close), but in this sentence it functions very much like an adjective.

So est fermée means is closed.

For a learner, the most useful way to understand it is:

• fermer = to close
• fermée = closed

French often uses être + past participle to describe a state:

• La porte est fermée. = The door is closed.
• La fenêtre est ouverte. = The window is open.

In normal English translation here, it means is closed.

It describes the current state of the door.

Depending on context, French être + past participle can sometimes suggest a resulting state, and sometimes something close to a passive meaning. But in a sentence like this, the natural understanding is simply:

• The back door of the house is closed.

Not has been closed.

est is the il/elle/on form of être, meaning is.

Since la porte arrière de la maison is singular, French uses the singular verb:

• est = is

So the structure is:

• La porte arrière de la maison = the back door of the house
• est = is
• fermée = closed

Sometimes French speakers do use expressions like la porte de derrière, especially in more everyday speech, to mean the back door.

But la porte arrière is a correct and clear way to say the rear/back door.

Very roughly:

• la porte arrière = the rear door / back door
• la porte de derrière = the door at the back / the back door

The exact choice can depend on style, region, and context.

A simple pronunciation guide would be:

la port ah-ree-air duh la may-zon eh fair-may

A few useful points:

• porte: the final -e is silent
• arrière: sounds roughly like ah-ree-air
• maison: the ending is nasal, not a full n sound
• fermée: the final -ée sounds like ay

Also, in normal pronunciation, there is no strong liaison between est and fermée here.

Yes, if the context already makes it clear which back door you mean.

For example:

• La porte arrière est fermée. = The back door is closed.

Adding de la maison makes it more specific:

• La porte arrière de la maison est fermée. = The back door of the house is closed.

So the longer version gives more information, but both are grammatically correct.

Not always.

Porte arrière works well for a literal rear/back door, but French may also use other expressions depending on context, such as:

• porte de derrière
• porte du fond in some situations

Also, English back door can have figurative meanings, and those would not necessarily translate with porte arrière.

So in this sentence, porte arrière is a literal physical door at the back of the house.