Translation:I prefer white roses to the red ones.
I would not make 'red' plural, as the construction you use has a missing noun - .'ones' which gives the plural.. In standard English, we don't often make our adjectives agree in number, as in 'white roses' in your example.
If I were to use your phrasing, I would say "I prefer white roses to red",
Thing is, the word 'rouges' in Duo's sentence is not an adjective, its function here is that of a (plural) NOUN. With a few exceptions, all French nouns need an article (or some other determiner) before them, and in this sentence the article is "hidden" in 'aux': à + (plural) definite article LES = aux + plural noun 'rouges'.
A great many examples of nouns derived from adjectives are also found in English, for example: American(s), juvenile(s), alien(s), delinquent(s), conservative(s), multiple(s), white(s), musical(s), ancient(s), blue(s) and... red(s). In modern English adjectives can be declined for number when they are used as substitutes for nouns (as in, "I prefer the reds", where "reds" is shorthand for "the red ones", which, by contextual implication, means "the red roses".
From someone on another forum I have since learnt that the correct grammatical term for instances where an adjective is used as if it were a noun (such as 'rouges' in DL's sentence): is a nominalised adjective, a.k.a. an adjectival noun and/or a substantive adjective. Ref: http://www.wisegeek.com/what-is-a-substantive-adjective.htm
Sorry, I wasn't at all clear above. Personally, I would say either "I prefer white roses over red ones" (a slightly unusual construction but perfectly acceptable) or the answer given by Duo. I would also say "I prefer white roses TO red ones"
With "I prefer white roses over red ones", the idea is one of generality - in general, that is my preference. In the translation given by Duo, I get the sense of particular roses: that in this case, the white roses are preferable.
Although "instead of" is sometimes used with "prefer", especially in conversation, this is not really correct use of the phrase. It does depend on the region - perhaps it is more widely used in North America. Prefer should be used with "to" when using nouns in a simple sentence.
I will try and explain the difference as I see it :
"Instead of" really means "in place of" - more like the french "A la place de" or "in lieu" (also used in english) so...
"Instead of" is used when one thing is "replaced" by another,
"prefer…to" is used to express a preference for one thing over another.
so it's a matter of "using an alternative" versus "expressing a preference"
e.g. In France they eat croissants instead of cereal for breakfast In France they prefer croissants to cereal for breakfast.<pre>
I will buy the white roses instead of the red ones. I prefer white roses to red ones. I will use "instead of" instead of "to" if I want to I prefer "instead of" to "to" (even though it may not be quite right) :)</pre>
As language evolves, these conventions do change, but "prefer …to" is more correct than "prefer…instead of" when making a direct statement expressing a simple preference and if two nouns are involved - at least where I come from :)
"over" is less widely used but an acceptable alternative depending on the region
It's not that you shouldn't address this type of thing. That stop-the-clutter message has more to do with the fact that someone brings something up, many other people address the issue (at times in great detail), and then someone (or even one person after another) comes along and asks/addresses that very/same issue/question that has already been discussed/addressed. A surprising number of people do that alas..
For example, say someone comes along a week from now and asks "why not 'instead of?"... Well, n6zs already answered that question. So Duo is just requesting to stop unnecessary clutter.
You could if you wanted to, but it's not necessary and it wouldn't be as direct a translation (there is only one "roses" in the french). In English, "Ones" is there instead of "roses", but actually in English, it is quite acceptable to say I prefer the white roses to the red (just as the French is constructed - "roses" sous-entendu)
Liaisons are reserved for words starting with a vowel or a non aspirate H:
aux (Z) oranges, aux (Z) amis, aux (Z) hommes.
Liaisons have a reason for being: easing pronunciation by avoiding vowel conflicts. If there is no conflict between two vowel sounds (one finishing a word and the other one starting the next word), you don't need a liaison.
Why de? The example given is "je préfère les roses rouges aux blanches".
"aux" is a contraction of à + les.
So the general construction is "préférer à":
- je préfère ma soeur à ma voisine
- je préfère le lait à la bière
- je préfère l'eau au vin (à+le)
- je préfère un homme à un singe
- je préfère les rouges aux blanches