A viagem foi maravilhosa.

A is the feminine singular definite article, meaning the.

In a viagem, the noun viagem is feminine, so it takes a, not o.

• a viagem = the trip
• uma viagem = a trip

In Portuguese, every noun has a grammatical gender, usually masculine or feminine. Viagem happens to be a feminine noun, so it uses feminine articles and adjectives:

• a viagem maravilhosa
• uma viagem longa

This is something you usually just learn together with the noun: a viagem, not just viagem by itself.

Adjectives in Portuguese usually agree with the noun they describe in gender and number.

Since viagem is feminine singular, the adjective must also be feminine singular:

• a viagem maravilhosa = feminine singular
• o filme maravilhoso = masculine singular
• as viagens maravilhosas = feminine plural
• os filmes maravilhosos = masculine plural

Foi is the third-person singular form of the verb ser in the pretérito perfeito (simple past).

Here it means was:

• A viagem foi maravilhosa. = The trip was wonderful.

It is used because a viagem is singular, and the speaker is talking about a completed trip in the past.

This is a very common question. Both can sometimes translate as was, but they are used differently.

• foi (from ser, preterite) presents the trip as a completed event, often with a clear overall evaluation.
• era (from ser, imperfect) sounds more like background description, repeated context, or an ongoing past state.

So:

• A viagem foi maravilhosa. = The trip was wonderful.
  This is the normal way to sum up a finished trip.

• A viagem era maravilhosa.
  This sounds less natural in most situations, unless you are describing how it used to be from some past perspective or setting a scene in a narrative.

For a simple statement about a completed trip, foi is the better choice.

Yes, but it means something slightly different.

• foi maravilhosa gives a general judgment about the whole trip.
• estava maravilhosa suggests a temporary condition or how it was at a certain moment.

Compare:

• A viagem foi maravilhosa. = The trip was wonderful.
• A viagem estava maravilhosa até começar a chover. = The trip was wonderful until it started raining.

So foi maravilhosa is the more natural sentence if you are simply evaluating the trip afterward.

In Brazilian Portuguese, viagem is roughly pronounced like vee-AH-zhehng.

A few helpful notes:

• vi sounds like vee
• a is stressed here: vi-A-gem
• g before e sounds like the s in measure or the zh sound
• the final -em is nasal in Brazilian Portuguese

A rough English-friendly approximation is vee-AH-zhen or vee-AH-zheing, but with a nasal ending.

In Portuguese, adjectives usually come after the noun:

• a viagem maravilhosa
• um filme interessante
• uma cidade bonita

That said, some adjectives can also come before the noun, but the position can change the tone or emphasis.

For example:

• uma viagem maravilhosa = a wonderful trip

This is completely normal. In this sentence, though, the adjective comes after the verb because it is part of the description of the subject:

• A viagem foi maravilhosa.

Normally, no. In standard Portuguese, you would usually need the article here:

• A viagem foi maravilhosa.

Leaving out the article sounds unnatural in this sentence.

Portuguese uses definite articles more often than English does, so where English says Trip was wonderful only in a very informal note style, Portuguese normally still wants A viagem.

The structure is:

Subject + verb + adjective

• A viagem = subject
• foi = verb
• maravilhosa = adjective describing the subject

So the sentence literally works like:

• The trip
  • was
    • wonderful

Maravilhosa usually means wonderful, marvelous, or fantastic, depending on context.

It often feels a bit expressive or enthusiastic. In everyday speech, Brazilians also use other adjectives like:

• ótima = great
• incrível = incredible
• fantástica = fantastic

So A viagem foi maravilhosa sounds very natural and very positive.

It would become:

As viagens foram maravilhosas.

Here is what changed:

• a → as because the noun is now plural
• viagem → viagens
• foi → foram
• maravilhosa → maravilhosas

Everything agrees in number, and the adjective still agrees in gender as well.

Yes, very natural.

A viagem foi maravilhosa. is a normal, everyday way to say that a trip was wonderful. It sounds like something a native speaker would really say after coming back from a vacation or any kind of trip.