Они мечтали о рае.

Они means they. It is the nominative plural form of the pronoun.

Unlike English, Russian does not have a separate plural pronoun for different genders. So они can refer to:

• a group of men
• a group of women
• a mixed group
• even things or animals

You only learn the gender makeup from context, not from они itself.

Мечтали is the past tense plural form of the verb мечтать, which means to dream, to daydream, or to long for.

Russian past tense forms agree with gender and number, not person. Compare:

• я мечтал — I dreamed, masculine speaker
• я мечтала — I dreamed, feminine speaker
• оно мечтало — it dreamed
• они мечтали — they dreamed

So -ли here tells you the subject is plural.

It can mean any of those, depending on context.

Because мечтать is an imperfective verb, the past form мечтали often suggests:

• an ongoing action in the past — they were dreaming
• a repeated or habitual action — they used to dream
• a general past situation — they dreamed

Russian does not force the same tense distinctions that English does here. The wider context tells you which English translation fits best.

Because the verb мечтать normally uses о + prepositional case when you say what someone dreams about or longs for.

So the pattern is:

• мечтать о чём-то — to dream of/about something

That is why рай changes to рае after о:

• рай → о рае

This is very common in Russian. Many verbs and expressions require a specific preposition and case, and you simply learn them together.

Рае is the prepositional singular form of рай.

The noun рай ends in -й, and masculine nouns of this type often form the prepositional singular with -е:

• герой → о герое
• музей → о музее
• рай → о рае

So after о, you get о рае.

Grammatically, о often means about, but with мечтать English usually translates the whole expression as either:

• to dream about
• to dream of

So мечтали о рае can naturally become either they dreamed about paradise or they dreamed of paradise.

In other words, it is best to learn мечтать о as a set pattern, instead of translating о word-for-word every time.

Usually мечтать is more about wishing, longing, or daydreaming than about dreams during sleep.

So Они мечтали о рае most naturally suggests that they longed for paradise or imagined paradise, not necessarily that they saw it in a sleeping dream.

For literal sleeping dreams, Russian often uses other expressions, such as:

• видеть сон
• сниться

But in some contexts, English still translates мечтать as dream.

Рай can mean both, depending on context.

Common possibilities:

• paradise in a general or poetic sense
• the Garden of Eden
• heaven in a religious sense, especially the blessed place after death

So the exact nuance depends on the surrounding text. If the meaning has already been given to the learner, this sentence’s grammar still works the same either way.

Yes. Russian word order is flexible.

Они мечтали о рае is the most neutral order:

• они — subject
• мечтали — verb
• о рае — prepositional phrase

But you could also say:

• О рае они мечтали — puts more emphasis on paradise
• Мечтали они о рае — can sound more marked, contrastive, or literary

The core meaning stays the same, but the focus or emphasis changes.

The main stresses are:

• они́
• мечта́ли
• о ра́е

A learner-friendly breakdown would be:

• а-НИ
• меч-ТА-ли
• о РА-е

In о рае, the last part is pronounced as two syllables: РА-е, not as one single syllable.