Alleged misuse of the word 'respective'

Respective designates the one-to-one relationship between the corresponding members of two different sets of things. Thus, in the examples given in the comments to your question:

• "They chatted about their respective childhoods" — A chatted about her childhood and B chatted about his childhood. One set of chatters, one set of childhoods; for each chatter there is a corresponding childhood.
• "successful in their respective fields" — A was successful in her field, and B was successful in his field. One set of successful people, one set of fields; for each successful person there is a corresponding field.

EDIT:

And, as FumbleFingers points out, if you enumerate the two sets, the members must be named in the same order.

In your example, however, there is only one set of things, languages, and there is no other set of things to which the languages stand in a one-to-one relationship.

On this question you'll find some disagreement. Despite the core meaning provided by StoneyB, sometimes 'respective' simply means 'separate, several, particular', as is attested both by the dictionary and by a corpus search.

The trouble for a lot of people is that separate, several, particular and respective are all examples of a class of 'weak' words which are often technically redundant and merely bog down sentences. (To study this argument in greater detail as applied to "respective", look here.)

Examples of 'unnecessary' respective from the corpus search link:

Their respective shares of the vote in the first round of voting were: Les verts 4.01 per cent, Génération écologie 3.62 per cent.

The trust will also recommend whether the investment costs should be passed on to consumers (a decision ultimately the responsibility of the respective regulatory bodies).