Adivina la carta roja.

Here it is a command: Adivina = Guess.

Spanish adivina can also mean he/she guesses or you guess in the present tense, because the form is the same. Context tells you which meaning is intended.

In Adivina la carta roja, it sounds like someone is telling another person, informally, to guess the red card.

• tú command: Adivina
• él/ella/usted present: adivina

So this sentence is using the informal singular command form.

Because Spanish often leaves out subject pronouns when they are understood from the verb form or from context.

In English, you must say Guess the red card with an implied you. In Spanish, the command form already shows that someone is being addressed, so tú does not need to appear.

You could say Tú, adivina la carta roja for emphasis, but normally that would sound unnecessary.

La means the, and it tells you that the speaker has a specific red card in mind.

So:

• la carta roja = the red card
• una carta roja = a red card

Spanish uses articles very often, sometimes more often than English. In this sentence, la makes the object definite and specific.

In Spanish, descriptive adjectives usually come after the noun.

So:

• la carta roja = the red card

This is the normal order. English usually puts the adjective first, but Spanish often puts it after the noun.

Putting roja before the noun would sound unusual here and would not be the normal way to describe a card’s color.

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

Carta is a feminine singular noun, so the adjective must also be feminine singular:

• carta roja = feminine singular
• cartas rojas = feminine plural

If the noun were masculine singular, you would use rojo instead.

The article tells you: la carta.

Also, nouns ending in -a are often feminine, though that is only a general pattern, not a perfect rule.

So here:

• la carta = feminine
• therefore roja must also be feminine

It can mean both, depending on context.

Common meanings of carta include:

• letter
• card
• sometimes even menu in some contexts

In this sentence, the intended meaning is clearly card, because you are being asked to guess which card is red.

Because the most natural Spanish structure is:

• article + noun + adjective
• la carta roja

Spanish usually does not put a descriptive color adjective before the noun in ordinary speech. So la roja carta sounds marked, poetic, or unnatural in normal conversation.

For a beginner, the safest pattern is:

• el libro azul
• la casa blanca
• la carta roja

Yes. Adivina is the informal singular command used with tú.

If you were speaking more formally, with usted, you would say:

• Adivine la carta roja.

So:

• Adivina = command to tú
• Adivine = command to usted

This is an important distinction in Spanish.

The negative tú command is different from the positive one.

So:

• Adivina la carta roja. = Guess the red card.
• No adivines la carta roja. = Don’t guess the red card.

Notice that the negative tú command uses the present subjunctive form:

• positive: adivina
• negative: no adivines

A common Latin American pronunciation is roughly:

• ro-ja → RO-ha

The j sound in roja is like a strong English h, but often a bit rougher.

A simple learner-friendly approximation is:

• roja ≈ RO-ha

Also:

• the r in roja is a single tapped r
• the j is not like the English j in job

Grammatically, yes, because carta can mean letter too. But in normal usage, context decides.

If someone is showing playing cards, flashcards, or colored cards, la carta roja will naturally mean the red card.

So the grammar allows both, but the situation usually makes the meaning clear.

Yes, it is natural and understandable.

It sounds like a simple instruction, especially in a game, classroom activity, or guessing exercise.

Depending on the exact situation, a native speaker might also say things like:

• Adivina cuál es la carta roja. = Guess which one the red card is / Guess which is the red card.
• Adivina qué carta es la roja.

But Adivina la carta roja is perfectly fine as a short, direct instruction.