L'armari de sota és buit.

Because the masculine singular definite article el usually shortens to l' before a vowel sound.

So:

• el armari → l'armari

This is very common in Catalan:

• l'home = the man
• l'escola = the school
• l'amic = the friend

So l'armari simply means the cupboard / the wardrobe / the cabinet, depending on context.

Armari is a general word for a piece of furniture used for storage. Depending on context, it can mean:

• cupboard
• cabinet
• wardrobe
• closet

So in this sentence, the exact English word depends on what kind of armari is being talked about. If the meaning has already been given to you, then just remember that armari is a fairly broad storage-furniture word.

De sota means the one below, underneath, or from below / lower depending on context.

In l'armari de sota, it identifies which cupboard/cabinet you mean:

• l'armari de sota = the cupboard below / the lower cupboard

It is a very natural way in Catalan to refer to something by its position relative to something else.

Because de sota is a common Catalan expression used after a noun to mean the one underneath/below.

Compare the idea in English:

• the cupboard below
• the cupboard underneath

Catalan often uses:

• de sota = below / underneath
• de dalt = above / upstairs / on top

So:

• l'armari de sota = the lower cupboard
• l'armari de dalt = the upper cupboard

Using just sota after the noun would sound less natural in this kind of phrase.

Because armari is masculine singular, and the adjective must agree with it.

Here are the forms of buit (empty):

• buit = masculine singular
• buida = feminine singular
• buits = masculine plural
• buides = feminine plural

So:

• L'armari ... és buit. = The cupboard is empty.
• La capsa ... és buida. = The box is empty.
• Els armaris ... són buits. = The cupboards are empty.

You mainly know it from the article:

• l'armari could come from el armari, so it is masculine singular

Also, dictionary entries normally show the gender. With nouns ending in -i, gender is not always obvious just from the ending, so it is best to learn the noun together with its article:

• l'armari / un armari

That helps you remember both meaning and gender.

És means is, from the verb ser (to be).

So:

• L'armari de sota és buit. = The cupboard below is empty.

The accent is important because és is different from es.

• és = is
• es = a pronoun, like himself/herself/itself in some contexts

The accent helps distinguish them in writing.

This is normal in Catalan. After ser (to be), the adjective comes after the verb, just as in English:

• is empty
• és buit

So the structure is:

• subject: L'armari de sota
• verb: és
• adjective: buit

This is completely standard Catalan word order.

A simple approximate pronunciation for an English speaker is:

lar-MA-ree de SO-ta es BWIT

A few details:

• l'armari: the r is tapped/flapped, not like a strong English r
• és: sounds like es in best, but shorter and cleaner
• buit: roughly bwit, one syllable for many speakers

A more IPA-style guide is approximately:

/l arˈmaɾi də ˈsɔ.tə ˈbwit/

Pronunciation varies a bit by dialect, but that is a good starting point.

Yes. The exact English translation can vary a little depending on the situation.

L'armari de sota could mean:

• the cupboard below
• the lower cabinet
• the wardrobe downstairs
• the cabinet underneath

The basic idea is always that it is the armari that is lower than another one or in the lower position. Context tells you the most natural English choice.

Yes, but L'armari de sota és buit is very natural.

Other possibilities might exist depending on style or context, for example with a more formal adjective such as inferior, but that would often sound less everyday. In ordinary speech, Catalan commonly uses position phrases like:

• de sota = below
• de dalt = above

So for a learner, this sentence is a very useful everyday pattern to remember.