Learn Hardcore Chinese: tā shì wǒ de nǚ tóngxué.

的 is a structural particle that links a modifier to a noun. Here it links the possessor 我 (I/me) to the noun phrase 女同学 (female classmate).

So:

我 + 的 + 女同学 ≈ my + female classmate

More generally:

我的书 – my book
他的老师 – his teacher
上海的天气 – Shanghai’s weather

It can mark possession (my, your, his…) or more general “of” relationships (Shanghai’s weather, China’s history, etc.).

Can I leave out 的 and say 她是我女同学?

Yes, you can say:

她是我女同学。

That sounds natural in everyday speech.

Nuance:

她是我的女同学。 – a bit more neutral/complete, works in both spoken and written Chinese.
她是我女同学。 – a bit more colloquial/compact.

In general, with short personal pronouns (我、你、他/她) plus certain human nouns (like 同学, 同事, 朋友), 的 is often omitted in conversation:

我(的)同学
你(的)朋友

Both versions are acceptable; including 的 is always safe.

Why is there 女 before 同学 if 她 already shows it’s a woman?

In writing:

他 – he
她 – she

So in characters, the gender is clear.
But in speech, both are pronounced tā, so you can’t hear the difference.

Adding 女 makes the gender explicit or emphasizes it:

她是我的同学。 – She is my classmate. (gender not highlighted)
她是我的女同学。 – She is my female classmate. (gender is relevant/emphasized)

You’d especially add 女 when:

you’re contrasting male vs. female classmates, or
gender matters in the context (e.g. talking about dorms, roommates, quotas, etc.).

If gender is not important, 她是我的同学 is more common.

What’s the difference between 同学 and 学生?

学生 – student (focuses on the role: a person who studies)
同学 – classmate / schoolmate (focuses on same school/class as you)

So:

她是学生。 – She is a student. (somewhere)
她是我的同学。 – She is my classmate (we study at the same school/class).

In 她是我的女同学, 同学 specifically encodes the “same school/class as me” idea.

Could I say 她是我的一个女同学? When do I need 一个?

Yes:

她是我的一个女同学。 – She is one of my female classmates.

Here 一个 (yí gè) is a measure word + number, highlighting that she is one among several.

Use 一个 when you want to stress:

one of many: 他是我的一个老师。 – He is one of my teachers.
a single instance: 给我一个苹果。 – Give me an apple.

Without 一个:

她是我的女同学。 – Just identifies her as my female classmate, no emphasis on “one of many.”

Why don’t we need a plural marker like 们 in 女同学 if we might mean “classmates”?

同学 (and 女同学) can be singular or plural depending on context.

她是我的女同学。 – She is my female classmate. (singular)
她们是我的女同学。 – They are my female classmates. (plural subject)

If you want to explicitly say “female classmates” (plural), you can use:

她们是我的女同学。 (They are my female classmates.)
Or: 她们是我的女同学们。 (also grammatical, but 们 after 同学 is mainly used when addressing a group: 同学们，好！ – “Hello, students!”)

In identity sentences, Chinese often relies on context for singular/plural rather than marking it on the noun.

How would I say “They are my female classmates” using this pattern?

Just make both the subject and pronoun plural:

她们是我的女同学。
- 她们 – they (female)
- 是 – are
- 我的 – my
- 女同学 – female classmates

Because the subject is clearly plural (她们), 女同学 is understood as classmates without changing its form.

Is the word order always Subject + 是 + 我的 + (女)同学? Could I say 我是她的女同学 instead?

Yes, you can say:

我是她的女同学。 – I am her female classmate.

The basic pattern is:

Subject + 是 + Predicate-Noun

So you can choose which person is the subject:

她是我的女同学。 – She is my female classmate.
我是她的女同学。 – I am her female classmate.

Both are correct; you just switch perspective.

What’s the difference between 同学 and 朋友 in a sentence like this?

同学 – classmate/schoolmate (relationship based on studying together, same class/school)
朋友 – friend (much broader: anyone you’re on friendly terms with)

For example:

她是我的同学。 – She is my classmate.
她是我的朋友。 – She is my friend.
她既是我的同学，也是我的朋友。 – She is both my classmate and my friend.

You’d choose 同学 here because the sentence is specifically about a school/class relationship.

How do I pronounce 女 (nǚ) correctly? The ü sound is confusing.

女 is pronounced nǚ (third tone).

To make the ü sound:

Say “ee” as in see (tongue high and front).
Without moving your tongue, round your lips as if saying “oo”.
You’ll get a sound between English ee and oo – that’s ü.

So:

女 (nǚ) – third tone: start mid, dip down, then rise (a low, “dipping” tone of moderate length).

When is 是 omitted in Chinese? Could I ever drop it in a sentence like this?

In identification sentences with nouns/pronouns like this one, you normally keep 是:

她是我的女同学。 ✅
她我的女同学。 ❌ (incorrect)

Common cases where 是 is omitted:

Before adjectives:
- 她很忙。 – She is busy. (no 是)
- 天气很冷。 – The weather is cold.
In some fixed, short patterns with 是…的 omitted, or in headlines/slogans, but that’s more advanced.

For beginner/intermediate usage:
If it’s “A is B” (both nouns/pronouns), use 是.

Does 我的 here mean “my” or “mine”? Chinese just uses the same form?

Yes, 我的 can correspond to both my and mine, depending on position.

Before a noun: 我的女同学 – my female classmate
Alone as a noun phrase:
- 这是我的。 – This is mine.

In 她是我的女同学, 我的 is functioning like “my” (attributive), but grammatically it’s just 我 + 的: “the one that belongs to me / related to me.” Chinese doesn’t have separate forms like my vs mine; 的 covers both uses.

Is 她是我的女同学 formal, informal, or neutral?

It’s neutral and works in most situations:

Answering “Who is she?”
Introducing someone to a teacher or colleague
Writing a simple description in an email or short text

In very casual speech, people might shorten it to:

她是我女同学。 (dropping 的)

Both are fine; the original sentence is safe in almost any context.