A French conversation rarely flows in a straight line. Speakers jump between topics, recall things, drop in side comments, and circle back. The markers that signal these shifts — au fait, à propos, à propos de, en passant — are essential to native-sounding speech, and each handles a different kind of shift. Au fait introduces a related-but-new topic. À propos picks up something just mentioned. À propos de points to a specific subject. En passant slips in a remark while continuing the main thread. Add the very colloquial tiens and you have the whole topic-shifting toolkit.
A learner who masters only au fait and à propos will already sound dramatically more native. This page sorts them out, pins down the pronunciation traps, and shows the pragmatic effect of each.
The headline summary
| Marker | Core function | Pragmatic flavour | Register |
|---|---|---|---|
| au fait | by the way | introduces related new topic | neutral, very common |
| à propos | while we're on the subject | picks up on what was just said | neutral |
| à propos de | regarding, about | specifies the topic | neutral |
| en passant | in passing, by the way | secondary remark within main thread | neutral/slightly formal |
| tiens | oh, hey | spontaneous topic shift | informal/spoken |
A working rule: au fait introduces a new but related topic, à propos picks up on the current one, à propos de points to a specific subject, en passant slides a remark in without taking over.
Au fait: by the way
Au fait is the most-used topic-shifter in spoken French. It introduces a topic that is related to but distinct from what was just being discussed — a sudden recollection, a related question, an aside. English by the way is the closest equivalent.
Au fait, tu connais Marie ?
By the way, do you know Marie?
Au fait, j'ai oublié de te dire — Pierre arrive demain.
By the way, I forgot to tell you — Pierre is arriving tomorrow.
Au fait, comment s'est passé ton entretien ?
By the way, how did your interview go?
The pragmatic function is to add a topic without abandoning the main thread. After the parenthetical, the conversation can either pursue the new topic or return to the original.
Critical pronunciation: the t is pronounced
The single most common mistake learners make with au fait is mispronouncing it. Most French words ending in t go silent — fait on its own, in the noun un fait (a fact), can be pronounced /fɛ/ or /fɛt/ depending on speaker. But in the discourse marker au fait, the t is always pronounced: /o fɛt/.
Au fait, tu viens ce soir ?
By the way, are you coming tonight? — pronounced /o fɛt ty vjɛ̃ sə swaʁ/
Au fait as the point
There is a second use of au fait that has nothing to do with topic-shifting: in the expression aller au fait or en venir au fait — to get to the point.
Bon, j'en viens au fait.
Right, I'll get to the point.
Allons droit au fait.
Let's go straight to the point.
Mettre quelqu'un au fait de quelque chose.
To bring someone up to speed on something.
In these expressions, fait keeps its noun meaning (the fact, the point) and the t may or may not be pronounced depending on speaker. These are unrelated to the discourse marker.
À propos: while we're on the subject
À propos is similar to au fait but pragmatically distinct. It picks up on something just mentioned and pivots into a related topic. Au fait says I just thought of something; à propos says that reminds me.
— Pierre arrive demain. — À propos, tu as vu sa nouvelle voiture ?
— Pierre is arriving tomorrow. — Speaking of which, have you seen his new car?
On parle d'argent. À propos, tu as remboursé Sophie ?
We're talking about money. Speaking of which, did you pay Sophie back?
À propos, comment va ta sœur ?
Speaking of which, how's your sister?
The diagnostic test: if the new topic is triggered by the previous one, à propos is natural. If you are bringing up something you just remembered, unrelated to the immediate context, au fait is the better choice.
À propos in writing
In written French, à propos without a complement (de [topic]) is rare. Writers tend to use à propos de with an explicit topic. The bare à propos belongs primarily to spoken French.
À propos de: about, regarding
À propos de introduces a specific topic with a noun phrase or pronoun. It is the most explicit topic-shifter — you state exactly what you want to talk about.
À propos de Pierre, il m'a appelé hier.
About Pierre — he called me yesterday.
À propos de la réunion, on la décale à 15h.
Regarding the meeting, we're moving it to 3pm.
À propos de ça, j'ai une question.
Regarding that, I have a question.
The structure is fixed: à propos de + noun (or pronoun ça / cela). Note that à propos de contracts as expected with the article: à propos du (de + le), à propos des (de + les).
À propos du projet, il faut qu'on en parle.
Regarding the project, we need to talk about it.
À propos des vacances, vous partez quand ?
About the holidays, when are you leaving?
À propos de in writing
In writing, à propos de is the standard way to introduce a topic in headings, subject lines, and structured text. It is neutral in register and works in any context.
À propos de cet article, j'aimerais ajouter une remarque.
Regarding this article, I would like to add a remark.
Note : à propos des frais d'inscription, voir page 12.
Note: regarding registration fees, see page 12.
En passant: in passing
En passant signals a remark that is deliberately secondary — the speaker is not abandoning the main thread, just dropping in a comment along the way. English in passing, as an aside captures the flavour.
Je note en passant que les chiffres sont contestables.
I note in passing that the figures are questionable.
Il a mentionné, en passant, qu'il déménageait.
He mentioned, in passing, that he was moving.
J'ajouterai, en passant, que je n'étais pas d'accord.
I'll add, in passing, that I didn't agree.
The pragmatic effect is one of understatement — the speaker is signalling that the remark is incidental, even when (often) it isn't. En passant is slightly more formal than au fait and is comfortable in writing, speeches, and structured discussions.
Position
En passant typically sits inside the clause, between commas, rather than at the start. This positioning reinforces its pragmatic role: it interrupts but does not take over.
Le rapport, en passant, mentionne plusieurs erreurs.
The report, in passing, mentions several errors.
Cela dit en passant, c'est lui le responsable.
As an aside, he's the one in charge.
The fixed phrase cela dit en passant (said in passing) is a slightly bookish but common variant.
Tiens: the spontaneous oh
Tiens is the imperative of tenir (to hold) — here, take this — but as a discourse particle it has lost its verbal meaning entirely and become a marker of spontaneous shift. It signals: something just struck me, here it is.
Tiens, ça me fait penser, tu as vu Paul récemment ?
Oh, that reminds me, have you seen Paul recently?
Tiens, j'ai oublié de te dire !
Oh, I forgot to tell you!
Tiens, voilà mon frère qui arrive.
Oh, here comes my brother.
Tiens is (informal/spoken) and almost never written outside dialogue. It is one of the most reliable markers of native-sounding speech — learners who do not use it stand out as overly formal.
Tiens, tiens — the suspicious one
Doubled tiens, tiens is a separate expression meaning well, well — surprise mixed with mild suspicion or knowing irony.
Tiens, tiens, qu'est-ce que tu fais ici ?
Well, well, what are you doing here?
Tiens, tiens... il est encore en retard.
Well, well... he's late again.
This use has a clear sarcastic flavour. Most native speakers will recognise it from films and television.
Side-by-side comparison
The same conversational shift realised with each marker:
Au fait, tu as parlé à Sophie ?
By the way, did you talk to Sophie? (just remembered)
À propos, tu as parlé à Sophie ?
Speaking of which, did you talk to Sophie? (triggered by what was just said)
À propos de Sophie, tu lui as parlé ?
Regarding Sophie, did you talk to her? (specifying the topic)
J'ajoute, en passant, que tu pourrais parler à Sophie.
I'll add, in passing, that you could talk to Sophie. (incidental remark)
Tiens, et Sophie, tu lui as parlé ?
Oh, and Sophie — did you talk to her? (spontaneous reminder)
All five are correct French and all introduce or reintroduce Sophie as a topic. The choice depends on how the shift relates to the previous discourse: spontaneous (tiens), suddenly recalled (au fait), triggered by context (à propos), specifically addressed (à propos de), or incidentally inserted (en passant).
Combined and stacked markers
In casual speech, learners will often hear topic-shifters combined or stacked:
Tiens, au fait, tu connais Marie ?
Oh, by the way, do you know Marie?
À propos, tiens, ça me fait penser...
Speaking of which — oh, that reminds me...
Au fait, à propos de Pierre, il a déménagé.
By the way, regarding Pierre, he's moved.
These combinations are unselfconsciously colloquial. Don't avoid them — they are how French actually sounds.
Au fait vs en fait — the most common confusion
The most frequent learner mistake is confusing au fait with en fait. They look similar but mean completely different things:
- au fait (/o fɛt/) = by the way — discourse marker, topic-shifter
- en fait (/ɑ̃ fɛt/) = in fact, actually — assertion of truth
Au fait, tu connais Marie ?
By the way, do you know Marie? (topic shift)
En fait, je connais Marie depuis dix ans.
In fact, I've known Marie for ten years. (asserting truth)
Both pronounce the final t of fait — that part is the same. The difference is the preposition: au (at the) vs en (in). Mistaking one for the other will derail your sentence completely.
❌ Au fait, je ne suis pas d'accord.
If meaning *actually*, this is wrong — should be *en fait*
✅ En fait, je ne suis pas d'accord.
Actually, I don't agree.
A useful diagnostic: if you can paraphrase as by the way, use au fait. If you can paraphrase as actually or in fact, use en fait.
Topic shifts in writing vs speech
Topic-shifters in spoken French are dominated by au fait, à propos, and tiens. In written French — emails, reports, letters — the dominant choice shifts to à propos de:
À propos de votre demande, nous vous confirmons que...
Regarding your request, we confirm that...
Concernant la réunion de jeudi, voici l'ordre du jour.
Concerning Thursday's meeting, here is the agenda.
In formal writing you will also see concernant (concerning), quant à (as for), and au sujet de (on the subject of). All are higher-register topic-introducers used in business and administrative writing.
Quant à moi, je préfère rester.
As for me, I'd rather stay.
Au sujet de votre lettre, voici ma réponse.
On the subject of your letter, here is my reply.
Common mistakes
❌ Au fait je ne suis pas d'accord avec ça.
*Au fait* means *by the way*, not *actually*; for *actually* use *en fait*
✅ En fait je ne suis pas d'accord avec ça.
Actually, I don't agree with that.
❌ Au fait /o fɛ/ tu viens demain ?
The *t* of *fait* is pronounced in *au fait* (the discourse marker)
✅ Au fait /o fɛt/ tu viens demain ?
By the way, are you coming tomorrow?
❌ À propos Pierre, il arrive ce soir.
*À propos* needs *de* before a noun
✅ À propos de Pierre, il arrive ce soir.
Regarding Pierre, he's arriving tonight.
❌ Cher Monsieur, au fait, je vous écris pour...
Register clash — *au fait* is conversational; in formal correspondence use *à propos de* or *concernant*
✅ Cher Monsieur, je vous écris à propos de...
Dear Sir, I am writing to you regarding...
❌ Tiens, je voudrais vous demander, Madame le Directeur...
*Tiens* is too informal for addressing a superior
✅ Madame la Directrice, j'aimerais vous demander...
Madam Director, I would like to ask you...
❌ À propos de ça, qu'est-ce que t'en penses ? — Au fait c'est compliqué.
The reply *au fait* would mean *by the way*; if you mean *actually* or *the fact is*, use *en fait*
✅ À propos de ça, qu'est-ce que t'en penses ? — En fait c'est compliqué.
What do you think? — Actually, it's complicated.
The first error — confusing au fait with en fait — is by far the most common. The second is the silent-t trap that betrays a non-native speaker. The third is forgetting the de required after à propos when introducing a noun. The fourth is using a casual topic-shifter in formal correspondence — French formal letters use concernant or à propos de, not au fait. The fifth is the same register problem with tiens.
Why topic management matters
Native French conversation contains far more topic shifts than English speakers usually expect — partly because French rewards verbal liveliness, and partly because topic-shifters function as rhythmic markers that keep a conversation moving. A learner who never uses au fait, à propos, or tiens sounds stiff and formulaic. Adding two or three of these markers per minute of speech is one of the fastest ways to sound more French.
Key takeaways
- Au fait introduces a related new topic (by the way) — the t is pronounced /o fɛt/.
- À propos picks up on what was just said (speaking of which).
- À propos de
- noun specifies the topic (regarding [X]).
- En passant slides in a secondary remark while continuing the main thread.
- Tiens is a spoken, informal marker for spontaneous shifts.
- Au fait (by the way) and en fait (actually) are different markers — do not confuse them.
- In formal writing, prefer à propos de, concernant, quant à, or au sujet de.
- Topic-shifters are essential for natural-sounding speech; learners who avoid them sound stiff.
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