El cuarto está completamente desordenado.

In Spanish, every noun has a grammatical gender: masculine or feminine.
Cuarto (room) is a masculine noun, so it takes the masculine article el.

• el cuarto = the room (masculine)
• la habitación = the room (feminine)

The gender is mostly arbitrary and must be memorized with the noun. The -o ending often (not always) signals masculine, so el cuarto is standard.

In Latin America, cuarto generally means room, and very often specifically bedroom, depending on context.

Examples:

• Estoy en mi cuarto. = I’m in my room / my bedroom.
• Tiene tres cuartos. = It has three rooms (often “three bedrooms” when describing a house/apartment).

Other words:

• dormitorio, recámara (Mex.), pieza (Chile, parts of the South Cone) also mean bedroom.
  So El cuarto está completamente desordenado will usually be understood as “The bedroom is completely messy.”

Ser (es) and estar (está) both translate as “to be,” but they are used differently:

• estar is used for temporary states or conditions and locations.
• ser is used for inherent characteristics, identity, time, etc.

A room being messy is considered a changeable condition, not a permanent trait, so you use estar:

• El cuarto está desordenado. = The room is (currently) messy.
• El cuarto es pequeño. = The room is small. (inherent characteristic)

That’s why the correct verb is está, not es.

The accent mark in está distinguishes it from esta (without accent):

• está = he/she/it is, you (usted) are (from estar)
• esta = this (feminine demonstrative adjective/pronoun)

Also, by normal stress rules:

• Words ending in a vowel, n, or s are stressed on the second-to-last syllable.
• “esta” would be stressed on ES-ta (first syllable).
• For “está”, we want the stress on the last syllable: es-TÁ, so we add an accent.

So está = /es-TÁ/ (“is”), esta = /ES-ta/ (“this [feminine]”).

Completamente is an adverb meaning “completely.”

It is formed from the adjective completo (complete) + the adverbial ending -mente:

• completo → completamente
• rápido → rápidamente (quickly)
• lento → lentamente (slowly)

In English, we usually add -ly to make adverbs (“complete” → “completely”).
In Spanish, you often add -mente to the feminine singular form of the adjective:

• clara → claramente
• segura → seguramente

Yes, but there is a slight nuance:

• muy desordenado = very messy
• completamente desordenado = completely / totally messy, no order at all

Both are natural, but completamente desordenado emphasizes that the mess is absolute or total, not just “very” messy.

Adjectives in Spanish must agree in gender and number with the noun they describe.

• cuarto is masculine singular → desordenado must also be masculine singular:
  • El cuarto está desordenado.

If the noun were feminine:

• La habitación está desordenada. (habitación = feminine)

So desordenado/a changes depending on the noun:

• el cuarto desordenado
• la casa desordenada
• los cuartos desordenados
• las habitaciones desordenadas

You can say “El cuarto está desordenado completamente”, and it is grammatically correct, but:

• El cuarto está completamente desordenado. is more natural and common.
• Placing completamente before the adjective desordenado sounds smoother and more idiomatic.

General tendency:

• Adverbs of degree like muy, bastante, totalmente, completamente usually go before the adjective:
  • muy bueno, totalmente diferente, completamente desordenado

They all relate to messiness, but not in the same way:

• desordenado = messy / untidy (things are not in their place)

  • Clothes on the floor, books everywhere, toys all over = desordenado.

• desorganizado = disorganized (more about lack of system/structure)

  • Files not labeled, no system in a closet or schedule = desorganizado.
  • You can say una persona desorganizada (a disorganized person).

• sucio = dirty (physically not clean)

  • Dust, stains, trash, bad smell = sucio.

The sentence El cuarto está completamente desordenado says the room is very untidy, but not necessarily dirty. It could be clean yet in chaos.

Yes, in everyday speech you’ll hear more colloquial expressions, for example:

• El cuarto está hecho un desastre. = The room is a total mess.
• El cuarto está patas arriba. (less common in some regions) = The room is upside down / a mess.
• El cuarto está todo desordenado. = The room is all messy.

Your sentence El cuarto está completamente desordenado is perfectly correct and natural, just a bit more neutral/formal than some colloquial alternatives.

Using the same structure:

• Mi cuarto está completamente desordenado.

Other common versions:

• Mi cuarto está todo desordenado.
• Mi cuarto está hecho un desastre. (very colloquial: “My room is a total disaster / wreck.”)

Yes, cuarto can mean both:

1. A room (noun):

   • El cuarto está desordenado. = The room is messy.

2. Fourth (adjective/ordinal number):

   • Vivo en el cuarto piso. = I live on the fourth floor.

Context almost always makes it clear which meaning is intended, so native speakers are not confused by this.