Dos manzanas y media

Dos manzanas y media
 

Two apples and a half or two and a half apples, I think the second one is the correct, but when in which cases can we use and a half because I ve heard it so many times.

Where have you heard it? The "and a half" must come before the noun. Only if the noun is ellipsed would you hear the "and a half" on its own.

set an example please.

How many hours do we still have to walk? Two and a half.

The expression two XXX and a half is just wrong. There does seem to be one exception, relating to time:

How long have you been here?
A year and a half :good:
One and a half years :good:

A month and a half :good:
One and a half months :good:

This is weird. I don't think there are other exceptions. :thinking:

That was the case where I saw it. So it was an exception, thank you.

And what about
One apple and a half or one and a half apples ?
I ask you because I heard sb say that after a unit it goes before noun.

I would say one and a have apples.

OK, thanks again.

Sorry to disagree, but I would say that both are correct forms.

There's nothing wrong with using 'an apple and a half', but I do agree that it's much more common to hear 'one and a half apples'. There is likewise nothing wrong with 'two apples and a half', but I hear 'two and a half apples' more frequently, as well.

The 'half', when it follows the noun, is not a number, but a noun. There's no reason why we can't use a noun after the coordinating conjunction 'and'. That's perfectly good grammar.

Buffffffffff, confusing, tantas cabezas tantas sentencias, many heads many whatever.

I think an apple and a half is better English, but as I wrote before, I would more commonly use one and a half apples.

As in all languages, there are often many ways of saying the same thing.