Они говорили наедине.

Говорили is the past tense plural form of говорить.

• говорить = to speak / to talk
• говорили = they spoke / they were talking / they used to talk, depending on context

In this sentence, the most natural sense is usually:

• they were talking
• or they talked

Because Russian past tense agrees with the subject in number (and in the singular, also gender), говорили is plural to match они.

Because the sentence is in the past tense.

Compare:

• они говорят = they are speaking / they speak
• они говорили = they were speaking / they spoke / they used to speak

The ending -ли is a standard marker of the Russian past tense plural.

This is a very common Russian aspect question.

• говорили is from говорить = imperfective
• поговорили is from поговорить = perfective

In this sentence, говорили presents the action as an activity in progress, a process, or simply a fact without emphasizing completion.

So:

• Они говорили наедине. = They were talking in private / They talked alone
• Они поговорили наедине. = They had a private talk / They talked privately and finished

Using поговорили would make the conversation sound more like a completed event. Using говорили is more neutral about duration and completion.

Наедине is an adverb meaning:

• in private
• alone together
• one-on-one
• with no one else present

So Они говорили наедине means that the two of them were talking without other people around.

A useful nuance:

• наедине often suggests privacy, not just physical aloneness

For example, two people can be in the same room as others and not be наедине. The word implies a private situation.

It is one word: наедине.

This is important because many learners want to split it into на + something, but in modern Russian you should simply learn it as a fixed adverb:

• наедине = privately / alone together

So write:

• Они говорили наедине.

not as two separate words.

In modern Russian, наедине is best treated as a fixed adverb, not as a normal preposition + noun combination that you actively analyze by case.

So for practical learning purposes:

• don’t try to decline it
• don’t treat на here the same way as in ordinary combinations like на столе or на стол

Just memorize наедине as a whole expression.

Yes, Russian often omits subject pronouns when the subject is clear from context.

So both are possible:

• Они говорили наедине.
• Говорили наедине.

The full version with они is useful when:

• you are introducing the subject
• you want contrast or emphasis
• the context does not already make the subject clear

Without context, Они говорили наедине is clearer.

Yes, Russian word order is flexible.

This sentence can be rearranged, for example:

• Они говорили наедине.
• Наедине они говорили.

The basic version Они говорили наедине is the most neutral.

If you move наедине earlier, it usually gives that idea more emphasis:

• Наедине они говорили = It was in private that they were talking

So the meaning stays similar, but the focus can shift.

It can absolutely mean talked in the broader sense.

Говорить often means:

• to speak
• to say
• to talk

In this sentence, because there is no direct object and the context is two people together, English talk is usually the most natural choice:

• They were talking in private

If you wanted to stress language production more literally, speak might work in some contexts, but talk is usually better here.

This is a useful distinction.

• наедине = alone together / in private
• вдвоём = the two of them / as a pair

So:

• Они говорили наедине emphasizes privacy
• Они говорили вдвоём emphasizes that there were two of them

Sometimes the ideas overlap, but they are not identical.

For example:

• Они сидели вдвоём = The two of them were sitting together
• Они сидели наедине = They were sitting alone together, in private

If your main point is nobody else was there, наедине is better.

It usually involves being alone with someone or face-to-face with someone, so it most naturally applies to a situation with two parties in private.

Very often you will see it in patterns like:

• наедине с кем-то = alone with someone

Example:

• Она хотела поговорить с ним наедине. = She wanted to talk to him in private.

In Они говорили наедине, the idea is that they were alone together.

It is a completely normal, complete sentence.

Russian often allows short, compact sentences where English might sometimes want a little more context. Here, nothing is missing grammatically:

• Они = subject
• говорили = verb
• наедине = adverbial expression

So the sentence is fully natural as it stands.