Если не сегодня, то завтра мы встретимся в парке.

In Russian, если ..., то ... is a very common pairing, similar to if ..., then ... in English.

So:

• Если не сегодня, то завтра = If not today, then tomorrow

The word то is often optional in Russian, but it is very natural here because it clearly sets up the contrast between the two options.

There are two commas because the sentence contains a conditional-style structure:

• Если не сегодня, то завтра, мы встретимся в парке.

More standard punctuation would usually be written as:

• Если не сегодня, то завтра мы встретимся в парке.

The main comma is before то, separating the if part from the rest:

• Если не сегодня, то завтра ...

Russian often uses commas more regularly than English to mark clause boundaries and set expressions like this.

Russian often leaves out words that are easy to understand from context.

In this sentence, the full idea is something like:

• Если мы не встретимся сегодня, то встретимся завтра.

But Russian naturally shortens this to:

• Если не сегодня, то завтра.

This is a very common and idiomatic way to say if not today, then tomorrow.

It means that one option may not happen, but the other one probably will.

So the sense is:

• If not today, then tomorrow
• One way or another, it will happen soon

It is not just a literal contrast between two days; it also suggests confidence that the meeting will happen.

Because Russian can form the future in two different ways, depending on aspect.

Встретимся is the perfective future of встретиться. Perfective verbs usually form the future with a single word:

• я встречу(сь)
• ты встретишься
• мы встретимся

So:

• мы встретимся = we will meet

This is different from imperfective verbs, which use быть + infinitive for the future:

• мы будем встречаться = we will be meeting / will meet regularly

The -ся is important because встретиться means to meet each other / to meet up.

Compare:

• встретить = to meet someone
• встретиться = to meet, to get together, to meet each other

In this sentence, the meaning is mutual: we will meet each other in the park. So встретимся is the natural choice.

Grammatically, мы is not strictly necessary, because the verb ending -имся already shows first person plural:

• встретимся = we will meet

So Russian could say:

• Если не сегодня, то завтра встретимся в парке.

Adding мы makes the subject explicit. It can sound a bit clearer, more neutral, or slightly more emphatic.

Because в парке means in the park, referring to location.

Russian uses different cases depending on whether you mean:

• location: в парке = in the park
• direction/movement toward: в парк = into the park / to the park

Here, the sentence is about where the meeting will take place, not movement into the park, so Russian uses:

• в + prepositional case → в парке

Because after в meaning in, Russian usually uses the prepositional case for location.

The noun changes like this:

• парк = park
• в парке = in the park

This -е ending is very common for masculine nouns in the prepositional singular.

Because сегодня and завтра are adverbs of time here.

They function like English today and tomorrow, so they do not change form in this sentence:

• не сегодня = not today
• завтра = tomorrow

Russian has many time expressions that act as adverbs and stay unchanged.

Yes. Russian word order is flexible, though some orders sound more natural than others.

The given sentence:

• Если не сегодня, то завтра мы встретимся в парке.

Other possible versions include:

• Если не сегодня, то завтра встретимся в парке.
• Мы встретимся в парке, если не сегодня, то завтра.
• В парке мы встретимся, если не сегодня, то завтра.

The original order sounds natural because it starts with the time contrast, which is the main idea.

Not quite.

• или сегодня, или завтра = either today or tomorrow
• если не сегодня, то завтра = if not today, then tomorrow

The second version sounds more reassuring and more certain that the meeting will happen one of those two days. It often suggests: don’t worry, it will happen soon.

A natural stress pattern would highlight the contrast:

• Если не сегóдня, то зáвтра мы встрéтимся в пáрке.

Likely stressed words:

• сегодня
• завтра
• встретимся
• sometimes парке, if the location is important

The strongest contrast is usually between сегодня and завтра.

The dictionary form is встретиться.

Breakdown:

• встрет- = root related to meeting
• -и- / -ть = infinitive ending
• -ся = reflexive/reciprocal marker

From that infinitive:

• встретиться = to meet, to meet up

And in this sentence:

• встретимся = we will meet

Yes, very often.

Even though it uses если (if), the sentence does not always feel like a formal logical condition. In everyday speech, it often means something like:

• If not today, then tomorrow — we’ll meet in the park.
• Maybe not today, but in that case tomorrow.

So it can express a flexible plan rather than a hard condition.