Honestly, if you just want the quick answer, it’s sœur. That’s the word for sister in French. But if you’ve ever actually tried to have a conversation in Paris or Montreal, you know that a dictionary definition is basically just the tip of the iceberg. Languages aren't math equations. You can't just swap one word for another and expect to sound like a human being.
There’s a specific "o-e" ligature in the spelling—sœur—which looks like the two letters are having a private conversation. It’s pronounced sort of like the "u" in the English word "fur," but with a bit more attitude. If you're talking to your actual sibling, or maybe just complaining about her to a friend, the way you use this word changes everything.
The Basics of Sœur and Its Weird Spelling
Let’s get the technical stuff out of the way. In French, nouns have genders. Every single one of them. Since a sister is female, the word is feminine: la sœur. If you have more than one, it becomes les sœurs. Simple enough, right?
Wait.
The spelling is where people usually trip up. That joined "oe" is called an e dans l'o (e in the o). You’ll see it in words like cœur (heart) and œuf (egg). If you’re typing on a standard English keyboard, most people just type "soeur" and call it a day. Autocorrect usually fixes it, but if you're writing a formal letter or an essay, you’ve gotta use the $œ$ symbol. It matters. It’s one of those tiny details that separates someone who used a translation app from someone who actually knows the language.
Pronunciation is the next hurdle.
Don't say "sewer." Please.
It’s a rounded sound. Round your lips like you’re going to say "o" but try to say "e." It’s tight. It’s quick.
Slang and What People Actually Say
Nobody really walks around saying "Ma sœur" in every sentence unless they’re being weirdly formal or maybe a bit dramatic. French is full of argot (slang).
If you want to sound like a local, you use frangine.
It’s the equivalent of saying "sis" or "sissy," but it doesn't sound as childish as the English versions sometimes do. You’ll hear it all over France. "C'est ma frangine" sounds infinitely more natural in a café than the textbook version.
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Then there’s the Verlan version. Verlan is that back-to-front slang where you flip the syllables of a word. It started in the suburbs of Paris and basically took over the country. For sœur, the Verlan is reus.
"C'est ma reus."
It’s cool. It’s casual. It’s also something you probably shouldn't say to your boss, but definitely something you'll hear in French rap or among teenagers in the Métro.
The Step-Sibling Situation
Families are messy. French reflects that.
If you’re talking about a half-sister (same dad, different mom, or vice versa), the term is demi-sœur.
But what about a stepsister? You know, the daughter of your step-parent who isn't biologically related to you? French uses the same word: demi-sœur. However, if you want to be technically precise about the "step" relationship through marriage, you might see belle-sœur.
Now, this is where it gets confusing. Belle-sœur also means sister-in-law.
Context is your only savior here. If I say "C'est ma belle-sœur," I could be talking about my brother’s wife, my husband’s sister, or my dad’s new wife’s daughter. Usually, the person you're talking to will figure it out based on who else you've mentioned, but it’s a weird quirk of the language. Literally, it translates to "beautiful sister."
It’s kind of a nice way to look at in-laws, honestly.
Using Sister in French Idioms
You can’t just learn the word; you have to see how it lives in the culture. French people love their idioms. They’re colorful, sometimes gross, and usually make no sense if you translate them literally.
Take the phrase "Sœur de lait" (Milk sister).
It sounds like something out of a medieval fantasy novel, but it refers to two unrelated children who were nursed by the same woman. In modern times, it’s mostly used to describe a bond so close it feels biological.
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Then you have the religious side. Just like in English, a nun is called a sœur. If you’re in a convent or a Catholic school, you’re going to be saying "Ma sœur" a lot. It’s formal, respectful, and very much still in use.
How to Talk About Your Sister Without Sounding Like a Robot
If you're describing your sister, you need more than just the noun. You need adjectives that actually agree with the gender.
- Ma grande sœur: My big sister (older).
- Ma petite sœur: My little sister (younger).
- Ma sœur aînée: My eldest sister.
- Ma sœur cadette: My younger/youngest sister.
Notice how the adjectives change? In French, the ending of the word often changes to match the feminine "sœur." You add an 'e' to the end of things. Grand becomes grande. It’s a rhythmic thing. Once you get the hang of it, the sentences start to have a specific flow.
A Note on "Sissy" and Terms of Endearment
If you’re actually talking to your sister, you might use a nickname.
Sœurette is a common one. It’s cute. It’s like adding "-ie" to the end of a name in English. It implies a sense of affection, though it can also be used sarcastically if she’s being annoying.
"Alors, sœurette, on a encore piqué mes fringues ?"
(So, sis, did you steal my clothes again?)
Common Mistakes to Avoid
The biggest mistake? Forgetting the possessive adjective.
In English, we might just say "Hey, sister!" In French, that sounds like you’re in a movie about the 1800s. You almost always use ma (my).
Also, watch the nasal sounds. If you don't get the "oeu" sound right, you might end up saying something that sounds like "sourd" (deaf) or "soir" (evening). Imagine telling someone "I’m going to see my evening" when you meant to say you’re visiting your sister. They’ll be confused. You’ll be embarrassed. It’s a whole thing.
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Another one: Soeur vs. Fille.
Don't laugh, but beginners do this constantly. Fille means girl or daughter. Sœur is sister. If you tell someone "J'ai une fille," they are going to congratulate you on being a parent. If you meant you have a sister, you’ve just accidentally aged yourself twenty years and gained a dependent.
Beyond the Literal Meaning
In French history and philosophy, "sisterhood" takes on a bigger meaning. Think of the French national motto: Liberté, Égalité, Fraternité.
Wait. Fraternité is brotherhood.
For a long time, there was a push to include Sororité (Sorority/Sisterhood) in political discourse. While Sororité isn't in the official motto, the word has seen a massive surge in use over the last decade, especially in French feminist movements.
Using sororité describes a bond between women that transcends blood relations. It’s about solidarity. If you’re reading French news or social media, you’ll see this word everywhere. It’s the "modern" way to talk about the concept of sisters.
Real-World Application: How to Practice
Don't just stare at the word on a screen. Use it.
- Identify the relationship: Is she older (grande) or younger (petite)?
- Pick your level of formality: Use sœur for strangers, frangine for friends, and sœurette for her.
- Check your possessives: It’s always ma, ta, or sa. Never mon.
- Listen for the "œu": Put on a French podcast or movie (like 8 Femmes—there are plenty of sisters in that one) and listen specifically for how they drop the word.
Language is about connection. Knowing how to say sister in French is just a tool to help you describe one of the most important relationships in your life. Whether you’re calling her a reus in the streets of Lyon or introducing your belle-sœur at a wedding in Bordeaux, the nuances matter.
Moving Forward with Your French
If you want to actually master this, stop treating it like a vocabulary list. Start thinking in terms of "identity."
Next time you think about your sister, don't just think "sister." Think ma sœur. When she texts you something annoying, mutter "sacrée frangine" under your breath. The more you attach the French word to the actual human being in your life, the faster it sticks.
Try this: write down three sentences about your sister (or a fictional one if you’re an only child). Use one formal term, one slang term, and one adjective.
- Ma petite sœur est très intelligente.
- Ma frangine habite à Lyon.
- J'adore ma sœurette.
Doing this small exercise moves the word from your "passive" brain (words you recognize) to your "active" brain (words you can actually use). That’s how you actually learn a language. No shortcuts. Just practice and a bit of "o-e" ligature.