Demi, moitié, etc = Half

I am afraid there is no grammatical explanation for this, it is stylistic. The French just tend to say "la moitié" more often than "une moitié".

According to the lesson, "la moitié de" means "half the [something]", and "une moitié de" means "one half of [something]". I'm not sure if this is also true in French, but in English I think you can only say "one half" if it is possible to separate the thing into two halves. A biscuit, a cake or an apple, say, can be cut or split into two, and you can eat one half and leave the other. But you can't do that with a bottle. You can eat one half of the biscuit (a KitKat for example), but you can't drink one half of the bottle.

Hi Stephen,

I am not entirely sure what your question is. But half my salary I would tranlate as "la moitié de mon salaire".

-- Chris (not a native speaker).

Hi Chris,

Me too, and that is the answer I gave. Not sure why it was marked as incorrect.

Can you post the full sentence? It might give a clue why one is considered correct over the other.

-- Chris.

Hi Graham, I don't think you can slice it that way. In my understanding it is perfectly OK to say, "Donnez-moi cette demi-baguette."

The distinction is with respect to using it as an adjective (demi/e) or a noun (la moitié).

Une demi-page est rouge. -- A half-page is red.
Une moitié de la page est rouge. -- One half of a page is red.

There are foten used colloquialisms and appreviated forms evolving around demi.

Il est six heures et demie. -- It is half past six.
This is an abbreviation of "...six heures ete une demi-heure".

On se renconte à demie. -- We are meeting at half-past. (This assumes an agreement about which hour one is talking).

Je voudrais un demi. -- I would like a half-pint of beer. (This works only colloquially  in a bar when ordering beer.)

-- Chris (not a native speaker).

Darn, again the typos....:

foten --> often.
appreviated --> abbreviated
ete --> et

-- Chris.

Hi Graham,

As Chris has already pointed out you will find examples of demi and moitié used with both definite and indefinite articles. I can see where the confusion occurs as in English you only have one word - half.

Demi will usually be used with other words except when you ask for a beer in a bar : Je voudrais un demi s'il vous plaît.

But normally it will be used before the noun it refers to to mean half of it, une demi-heure, une demi-bouteille, une demi-journée, une demi-portion, un demi-verre ... e.g. J'ai fait un demi-marathon, l'hotel est à formule demi-pension.

Moitié is a noun and here are some examples:

J'ai fini la moitié de mon travail , j'ai lu la moitié de mon livre, nous avons mangé la moitié du gateau ( you cannot use demi in that instance - moitié meaning half of that whole).

There are some interesting expressions using demi and moitié , like à demi /à moitié   which mean the same thing, half done.

e.g. une bouteille à demi pleine, un pot à demi plein , un mur à moitié peint, un travail à moitié fini

'Ma moitié' which means my better half, my soul mate, my spouse.

Hope this helps but not easy !

Hi Dragana,

the rule is this: when "demi" comes before the noun, it is always and invariable "demi". When it succeeds the noun, it changes according to the gender.

Une demi-heure. -- Half an hour.
Une heure et demie. -- One and a half hour.

-- Chris (not a native speaker).

Bonjour Tatiana !

Here there's a nuance of meaning between une demi-baguette and la moitié de [la] baguette.

Une demi-baguette means "one half of baguette" or "half a baguette": here it's a general characteristic of the object, as opposed to a full baguette.

La moitié de [la] baguette means "the half of baguette" or "half the baguette", implying that we're talking about a specific baguette here, of which you'd want half.

The sentence here could be heard in a boulangerie, where you would ask for half a baguette, hence une demi-baguette.

I hope that's helpful!

À bientôt !