Learn Hardcore Russian: Мой друг — мой ровесник, мы учились в одном классе. - My friend is my peer; we studied in the same class.

Мой ровесник = “someone who is my age”.
Он мой ровесник ≈ Он одного со мной возраста (“He is of the same age as I am”), but ровесник is shorter and more natural.

There is also a feminine form:

ровесник – male peer
ровесница – female peer

So Мой друг — мой ровесник means “My friend is the same age as me / my peer in age.”

Why is there a long dash — between Мой друг and мой ровесник?

In Russian, a dash is often used between two nouns in the nominative case when they are linked by an implied “is/are”:

Мой друг — мой ровесник.
Literally: “My friend — my peer (in age).”
Meaning: “My friend is my peer (in age).”

Russian usually omits the verb “to be” in the present tense (есть is not used in neutral modern speech), so the dash visually marks the connection:

X — Y = “X is Y”.

You could write it without a dash (Мой друг мой ровесник) in very informal text, but the dash is the standard, clear way to write it.

Why are both друг and ровесник in the same case (nominative)?

This is the classic “X is Y” pattern in Russian:

Subject: Мой друг – nominative case
Predicate noun: мой ровесник – also nominative case

In Russian, when you say “X is Y” and both X and Y are nouns, Y normally stays in the nominative, not in another case:

Он учитель. – “He is a teacher.” (both nominative)
Она моя сестра. – “She is my sister.” (both nominative)

So:

Мой друг — мой ровесник.
Subject: друг (nom.)
Predicative: ровесник (nom.)

Why is there a comma before мы учились в одном классе instead of и (“and”) or a semicolon?

Russian allows asyndetic coordination – joining clauses without a linking word like и.

Here we have two closely connected statements, side by side:

Мой друг — мой ровесник,
мы учились в одном классе.

You could add и:

Мой друг — мой ровесник, и мы учились в одном классе.

Both versions are correct. Without и, the comma simply separates two independent clauses that are logically related. English would more often use “and” or a semicolon:

“My friend is the same age as me; we studied in the same class.”

What does учились mean exactly, and what verb does it come from?

Учились is the past tense, plural form of the reflexive verb учиться.

учиться = “to study”, but more precisely “to be a student somewhere / attend some place of study / be in school (or university)”.
мы учились = “we studied / we were students (there) / we went to school (there).”

So мы учились в одном классе = “we were in the same class at school” or “we studied in the same class.”

Important distinction:

учиться (где?) – to study at a place (school, university):
Я учусь в школе. – I go to school / I’m in school.
изучать (что?) – to study a subject:
Мы изучали математику. – We studied mathematics.

Why учились and not учили?

Учили is from учить, which means “to teach” or “to learn/memorize something specific” depending on context.

Мы учили английский. – “We were learning (studying) English.”
Учитель учил нас. – “The teacher taught us.”

But учиться (reflexive) means “to study somewhere / to attend school/university.” That’s the meaning here:

Мы учились в одном классе. – “We were in the same class (at school).”

So учились (from учиться) is correct because the sentence talks about being classmates, not about learning a specific subject.

What exactly does в одном классе mean? Does одном mean “one” or “the same”?

Literally, в одном классе is “in one class”, but in this context it is idiomatic Russian for “in the same class (school class/grade)”.

So:

Мы учились в одном классе.
= “We studied in the same class (at school).”

Here одном really means “the same (single, shared)”, not “one out of many random classes.”

If you want to emphasize “the exact same class” even more, you can say:

Мы учились в одном и том же классе. – “We studied in one and the very same class.”

But in everyday speech, в одном классе already naturally means “in the same class (as each other).”

What is the grammar of в одном классе (cases and endings)?

В одном классе uses the prepositional case after the preposition в indicating location.

Breakdown:

класс (class) – masculine noun, nominative singular.
After в with a location meaning (“in”), класс → классе (prepositional singular).
один (one / a certain / the same) – masculine nominative:
In the prepositional masculine singular, it becomes одном to agree with классе.

So:

в одном классе
- в – in
- одном – “one/the same” (masc., prep. sg.)
- классе – “class” (masc., prep. sg.)

Together: “in the same class.”

Could I say одноклассник instead of ровесник? What is the difference?

Yes, but the meaning changes slightly.

ровесник – someone the same age as you (a peer in age).
They could be from another school, city, etc.
одноклассник – literally “classmate”, someone who is in (or was in) the same school class with you.

In your sentence:

Мой друг — мой ровесник, мы учились в одном классе.

This says:

He is my peer in age, and
We studied in the same class.

If you used одноклассник instead:

Мой друг — мой одноклассник. – “My friend is my classmate.”

That focuses on the fact that you share(d) a class, but says nothing directly about age (though normally classmates are roughly the same age).

Why Мой друг — мой ровесник, and not Мой ровесник — мой друг? Does word order matter?

Both are grammatically correct, but the word order affects emphasis:

Мой друг — мой ровесник.
Natural reading: “My friend (that I’m talking about) happens to be my peer in age.”
Focus: друг is the main topic; ровесник adds extra info.
Мой ровесник — мой друг.
Natural reading: “This person who is my peer in age is my friend.”
Focus: ровесник is the starting point; you are clarifying that he is not just any peer but specifically your friend.

In the original sentence, the main idea starts from “my friend”, so Мой друг — мой ровесник is more natural.

Is друг always “friend”, and is it masculine? What about a female friend?

Друг is grammatically masculine and usually refers to:

a male friend, or
in some contexts, a friend in general (gender-neutral in meaning but grammatically masc.).

For a specifically female friend, Russian commonly uses:

подруга – female friend.

So:

Мой друг – my (male or grammatically male) friend.
Моя подруга – my female friend.

You would normally not say мой друг about a clearly female person in everyday speech; you’d use моя подруга instead, unless you are making a special stylistic or ideological choice.

How are ровесник, учились, and классе pronounced and stressed?

Approximate pronunciation (stressed syllables in caps, IPA in brackets):

ровесник – ro-VYES-neek
Stress on ве: ровЕсник
IPA: [rɐˈvʲesʲnʲɪk]
учились – oo-CHEE-lees’
Stress on чи: учИлись
IPA: [ʊˈt͡ɕilʲɪsʲ]
классе – KLA-se
Stress on кла: клАссе
IPA: [ˈklassʲe]

Together:
Мой друг — мой ровесник, мы учились в одном классе.
[moj druk moj rɐˈvʲesʲnʲɪk mɨ ʊˈt͡ɕilʲɪsʲ v ɐdˈnom ˈklassʲe]