Which one to useB1

An vs année (and jour, soir, matin)

The short answer

The short form counts, the long form describes. An, jour, soir and matin go with numbers: trois ans, deux jours. Année, journée, soirée and matinée go with adjectives and describe the period as a stretch of time: une bonne année, toute la journée.

At a glance

An, jour, soir, matin or Année, journée, soirée, matinée?

CompareAn, jour, soir, matinA unit you count.Année, journée, soirée, matinéeA duration you describe.
With a numberAlways: trois ans, deux joursAlmost never
With an adjectiveRarelyUsually: une bonne année, une longue journée
What it namesA unit on the calendarThe time inside it, as experienced
GenderMasculineFeminine
Typical phrasel’an dernier, tous les jours, ce soirtoute la journée, bonne année, en soirée
With toutNot usedtoute la journée, toute la soirée

How to choose

Ask these, in order

  1. 1

    Is there a number in front of it?

    Short form. Numbers count units, and the short form is the unit.

    Elle habite ici depuis cinq ans.

    She’s lived here for five years.

  2. 2

    Is there an adjective describing the period?

    Long form. Bonne, longue, belle, mauvaise, entière all pull the long word.

    On a passé une très bonne soirée.

    We had a really nice evening.

  3. 3

    Are you saying “all” of it?

    Long form, with toute. The short form cannot take it.

    Il a plu toute la journée.

    It rained all day.

    NBTout le jour is not idiomatic. This is one of the clearest tests in the pair.

  4. 4

    Is it a fixed expression?

    Learn it as it is. L’an dernier, l’année dernière, bonne année, tous les jours all exist and several break the pattern.

    Bonne année ! et bonne santé.

    Happy New Year, and good health.

    NBBonne année, never bon an, even though a year is being counted off.

Side by side

Each one, in full

An, jour, soir, matin

The counting forms

A unit you count.

An, jour, soir and matin name units. They go with numbers, with quantities, and in the expressions that treat time as something ticked off: trois ans, quinze jours, tous les jours, ce soir, demain matin.

They are all masculine, which is a useful secondary check: if you have written une with one of them, something has gone wrong.

Le contrat court sur deux ans.

The contract runs for two years.

Je pars dans trois jours.

I’m leaving in three days.

On se voit ce soir ?

Shall we meet this evening?

NBCe soir points at a specific evening; cette soirée would describe how it went.

Année, journée, soirée, matinée

The describing forms

A duration you describe.

Année, journée, soirée and matinée treat the period as a stretch that was filled with something. They take adjectives, they take toute, and they are what you use when the period has a quality rather than a count.

All four are feminine, and all four carry the sense of duration: passer la journée, une matinée chargée, en soirée. If you can replace the English with “the whole of the…”, you want the long form.

J’ai passé la matinée en réunion.

I spent the morning in meetings.

Ça a été une année difficile.

It’s been a hard year.

Le musée est ouvert en soirée le jeudi.

The museum is open in the evening on Thursdays.

Mistakes to avoid

What learners actually get wrong

  • J’ai travaillé là-bas pendant trois années.

    J’ai travaillé là-bas pendant trois ans.

    A number takes the short form. Trois années is possible but marked, it emphasises the years as long, lived-through periods, which is rarely what a plain factual sentence wants.

  • Bon an !

    Bonne année !

    The New Year greeting takes the long form because it wishes you a good year, not one more year. This is the most-heard example of the pair and the one worth memorising outright.

  • Il a plu tout le jour.

    Il a plu toute la journée.

    Tout with a time word takes the long form. Tout le jour exists in older and poetic French and sounds wrong in ordinary speech.

  • L’année dernier

    L’an dernier / l’année dernière

    Both forms work here, but the adjective has to agree with the one you chose. Mixing a feminine noun with a masculine adjective is the giveaway, and it is easy to do while trying to get the noun right.

Questions

Asked and answered

Is an ever used with an adjective?
Yes, in a few fixed cases: l’an dernier, l’an prochain, le nouvel an, bon an mal an. These are set phrases rather than a pattern you can extend, and l’année dernière is equally correct and more common in speech.
Does the same rule cover jour and journée?
Exactly the same. Deux jours counts; toute la journée describes. Bonne journée as a farewell wishes you a good day, while tous les jours counts days off. Learning one pair well gives you all four.
What about matinée and soirée as events?
Both have a second meaning: une soirée is a party, and une matinée is a daytime performance, the sense English borrowed. Context separates them easily, and it is a good reminder that the long forms are about filled time rather than clock positions.