"Impersonal subject 'on'" 3A usually translated as "one", or informally as "you", "we", "they" or "people" depending on context.

What is the impersonal subject "on" in French?

The pronoun on is an indefinite (impersonal) subject pronoun. It refers to people in general, an unspecified agent, or — in everyday speech — to "we." Grammatically, on is treated as third person singular, so verbs are conjugated in the 3rd-person singular form.

Examples:
- On dit que Paris est belle. (People say that Paris is beautiful.)
- En France, on mange bien. (In France, people eat well.)
- On va au cinéma ce soir. (We/I'm/people are going to the cinema tonight.)

Choose the English equivalent by context: "on" = "one" (formal), "you"/"people" (general), or "we" (colloquial).

When and why do we use "on"?

Examples:
- On dit qu'il va pleuvoir. (People say it's going to rain.)
- On ne peut pas entrer sans badge. (You/people can't enter without a badge.)
- On apprend beaucoup à voyager. (One learns a lot by traveling.)

Examples:
- On part à huit heures. (We're leaving at eight.)
- On s'est rencontrhier. (We met yesterday.)
- On commence? (Shall we start?)

Examples:
- On m'a vol mon sac. (My bag was stolen / Someone stole my bag.)
- On m'a dit que tu viendrais. (I was told that you would come.)

Examples:
- On y va? (Shall we go?)
- On se calme! (Let's calm down / Everyone calm down.)

How is "on" formed and conjugated?

Present: on parle, on mange, on va
- On parle franais ici. (People speak French here.)

Imperfect: on parlait, on finissait
- Avant, on parlait plus souvent au tlphone. (Before, we/people used to talk on the phone more often.)

Future: on ira, on verra
- On ira demain. (We'll go tomorrow / People will go tomorrow.)

Conditional: on irait
- On irait si on avait le temps. (We/people would go if we had time.)

Subjunctive (after que): que l'on parte, que l'on fasse
- Il faut que l'on parte maintenant. (We must leave now.)

Note on agreement with compound tenses is discussed below (see "Agreement, possessives, and tricky cases").

Questions:
- Est-ce qu'on part maintenant? (Are we/people leaving now?)
- Qu'est-ce qu'on mange ce soir? (What are we going to eat tonight?)
- Que fait-on? (What does one do? — more formal: inversion is formal.)

Agreement, possessives, and tricky cases

However, when on clearly stands for a group of people (we), many native speakers use plural agreement in speech:
- On est contents. (Colloquial: We're happy.)

Recommendation: in formal or written French, prefer singular agreement or use nous to make plural agreement clear: Nous sommes contents.

With avoir, the past participle agrees only with a preceding direct object, regardless of on: Les chansons qu'on a chantes taient belles. (The songs that we sang were beautiful.) — here chantes agrees with les chansons, not with on.

Reflexive verbs are tricky. Standard written grammar prefers clarity:
- Colloquial: On s'est rencontr hier. (We met yesterday.)
- Formal/written: Nous nous sommes rencontrs hier. (We met yesterday.)
Many speakers say On s'est rencontrs in conversation; in formal writing, avoid ambiguity by using nous.

But when on means "we," native speakers often use our: notre/nos (or sometimes nos in speech):
- On a oubli nos parapluies. (Colloquial: We forgot our umbrellas.)

Recommendation: for clear, formal writing use nous + notre/nos. If you keep on and it refers to "we," choose the possessive that matches the intended natural person (our) to avoid confusion.

Comparing "on" with other subjects (il, nous, tu/vous, les gens)

Common mistakes and how to avoid them

Mistake: Wrong verb form (treating on as nous)
- Wrong: On allons au march.
- Correct: On va au march. (On takes 3rd-person singular: va, not allons.)

Mistake: Using on for weather or expressions that need impersonal il
- Wrong: On pleut.
- Correct: Il pleut. (Weather uses impersonal il.)

Mistake: Not contracting "que on"
- Wrong: Je sais que on arrive demain.
- Correct: Je sais qu'on arrive demain.

Mistake: Possessive mismatch leading to ambiguity
- Ambiguous: On a oubli son sac. (Whose bag?)
- Clear: Nous avons oubli notre sac. (We forgot our bag.) or On a oubli notre sac (colloquial, when on = we).

Mistake: Past-participle agreement errors in written French
- Prefer: On est parti. (standard written: singular) rather than On est partis (colloquial plural). In formal writing, use nous if you mean "we" and need plural agreement: Nous sommes partis.

Useful phrases and a comprehensive example set

Present and general statements:
- On travaille beaucoup ici. (People work a lot here.)
- On dirait qu'il est fatigu. (It seems that he's tired / You'd say he's tired.)

Questions and suggestions:
- Qu'est-ce qu'on fait ce soir? (What are we doing tonight?)
- On y va? (Shall we go?)

Negation:
- On ne fume pas ici. (You/people must not smoke here.)
- On n'a rien vu. (We/people didn't see anything.)

Pass compos and participle agreement:
- On a mang. (We ate / People ate.)
- On est arriv en retard. (We arrived late.) — standard singular.
- Les livres qu'on a lus taient intressants. (The books that we read were interesting.) — "lus" agrees with "les livres" (preceding direct object).

Reflexive verbs:
- On se voit demain. (We'll see each other tomorrow.)
- On s'est vus hier. (Colloquial: We saw each other yesterday.) — spoken plural agreement; in formal writing prefer: Nous nous sommes vus.

Subjunctive:
- Il faut que l'on parte tout de suite. (We must leave immediately.)

Conditional:
- On pourrait appeler, si tu veux. (We could call, if you want.)

Passive-like and reported speech:
- On m'a dit la vrit. (I was told the truth.)
- On m'a vol la voiture. (My car was stolen / Someone stole my car.)

Set phrases and proverbs:
- On verra. (We'll see. / One will see.)
- On ne sait jamais. (You never know.)
- On n'est jamais mieux servi que par soi-mme. (One is never better served than by oneself.)

If you want to be formally correct and clear in writing: replace on with nous when you mean "we," and use on for general, indefinite statements. In speech, using on is natural and very common.