El autorretrato retrata una cara seria.

Because autorretrato is a compound noun: auto- + retrato.

• auto- means self-
• retrato means portrait

So autorretrato = self-portrait.

Spanish often writes this kind of combination as a single word.

El is the masculine singular definite article, meaning the.

It appears here because autorretrato is:

• masculine
• singular
• being treated as a specific thing: the self-portrait

So:

• el autorretrato = the self-portrait

Because retrata is the verb, while retrato is a noun.

• retrato = portrait / portrait painting
• retratar = to portray
• retrata = he/she/it portrays

In this sentence, the subject is el autorretrato, which is third-person singular, so the verb must be retrata.

Conjugation of retratar in the present:

• yo retrato
• tú retratas
• él/ella/usted retrata

So El autorretrato retrata... is grammatically correct.

Yes, it is a bit repetitive, because autorretrato and retrata are closely related words.

It is still grammatical, but stylistically it can sound a little heavy or obvious, similar to saying something like The portrait portrays... in English.

A more natural alternative might be:

• El autorretrato muestra una cara seria.
• El autorretrato presenta una cara seria.

But the original sentence is perfectly understandable and useful for learning.

Because in Spanish, a singular countable noun usually needs an article or another determiner.

So Spanish normally says:

• una cara seria = a serious face
• la cara seria = the serious face

Leaving out the article would usually sound incomplete here.

In Spanish, adjectives often come after the noun.

So the normal order is:

• cara seria = serious face
• libro interesante = interesting book
• casa grande = big house

You can sometimes place adjectives before the noun, but that often changes the tone, emphasis, or style. In this sentence, cara seria is the normal and expected order.

Because adjectives must agree with the noun they describe.

Here, seria describes cara, and cara is:

• feminine
• singular

So the adjective must also be feminine singular:

• serio = masculine singular
• seria = feminine singular
• serios = masculine plural
• serias = feminine plural

Examples:

• un rostro serio
• una cara seria

Because seria here is the adjective serious, not a form of the verb ser.

This is an important difference:

• seria = serious (adjective, feminine singular)
• sería = would be (verb form, with accent)

So:

• una cara seria = a serious face
• sería una cara... would be something completely different grammatically

The accent mark changes both pronunciation and meaning.

It is the present indicative.

So retrata means:

• portrays
• depicts
• shows (depending on context)

In this sentence, it states a fact about what the self-portrait does.

In Latin American Spanish, rr is pronounced as a strong rolled or trilled r.

So in autorretrato, the rr is stronger than a single r between vowels.

A rough breakdown:

• au-to-rre-tra-to

The rr in autorretrato is the clearly trilled sound.
The r in retrata is not written rr, so it is not the same spelling pattern.

If you're a beginner, the key thing to remember is:

• rr = strong rolled r
• single r = usually a lighter sound

Yes. It follows the very common Spanish pattern:

• Subject + Verb + Object

Here that is:

• El autorretrato = subject
• retrata = verb
• una cara seria = direct object

So the structure is very straightforward and natural grammatically, even if the vocabulary is a bit repetitive stylistically.