It has always struck me that we linguists use different terminology to describe language skills (especially our own) than "lay people" and, in my CV at least, I now tend to exaggerate how well I speak all the languages I know compared to what I would say if I were speaking to a fellow linguist.

Even if we make a division between bilingual and fluent, actually quite few translators can be considered bilinguals, as only people who have been raised in a bilingual environment can be defined this way. The enormous 99.5 % left of people talking languages are just fluent (very good ones, but never bilingual).

I agree with both of you. People think I'm being modest when I say I'm not bilingual, but I'm really not (modest or bilingual). Like Olli, I think very few people are actually bilingual, but not everybody agrees; it's a hotly debated issue on translators' forums!

Interesting how we categorise thoughts about language. This debate offers me two boxes (fluent or bilingual) and implies that I need to know which box my command of my languages (native English, acquired German) belongs in.
But I feel that it is not so simple. I catch myself making mistakes in German, but I sometimes get my syntax twisted in English, too.
And when I speak German, I genuinely forget that it is not my "native" language, and the people I speak with don't notice, either. And as for written German, many adult native speakers regard me as an expert in the way their language should be written; they ask me things when they are uncertain, and they read my creative writing in German without even remembering that I am not a native speaker.
Perhaps one factor is that I have lived in the country of my non-native language for 25 years. And in some areas (especially everyday life), my German has overtaken my English. Céline, I would guess that this is in some ways similar to your proficiency in English.
So which box should I put myself in? And what's in a name anyway?

P.S. Céline, enjoy your coming break (saw your comment on Transblawg).

Victor, you're right to say that the "fluent or bilingual" choices are reductive, but the alternative is a great big muddle. This is where I stand: my (native English) copywriter friends in the office will consult me when they have doubts about something they're writing although English isn't my first language. That's because I studied English in greater depth than them, having had to make a conscious and concerted effort, over a number of years, to understand its mechanisms. I also feel that I can be myself to a more satisfying extent in English than in French.

However, there are mistakes I make in written English I'd never make in written French, and there is a level of intimacy, for want of a better word, I have with written French that I don't have (yet!) with written English. The other point is that bilingualism involves a deep knowledge of the culture a language belongs to, and there are also tons of cultural references I still miss in English.

I think the fact that your German has overtaken your English may be helped by the weakening of your English - feel free to write an outraged answer, in capital letters, to this if I'm completely wrong! I'm just very aware that I have to really work on my French to make sure it doesn't wither away for lack of everyday use, and I suspect it's a phenomenon most expats experience.

Does any of that make sense? I so need a break.

Interesting to try to work out what has happened/is happening to my languages (but no outrage and no all-caps reply).
In the areas that I work in frequently (contracts, architecture, property), my English is more active and I feel more expressive in English. And I feel very much at home with general written English in various forums on the web. But my everyday chit-chat in English is more like a written style (and my sister pulls my leg about it - whereas I get no such comments about my spoken or written German).
In German, I don't feel that there are cultural reference that I miss. And when I write (e.g. creative writing in a Christian setting and discussions in various translation forums) I can play around with different registers, styles and cultural references, and sometimes I actually have to explain such devices to native Germans.

I suppose if I had to choose a "little box", it would be the "bilingual box", but with stylistic imperfections in both. Which for me brings up the question of how perfect "native competence" is in any language. I would suspect that everyone who follows your blog and similar websites would score very highly in "native language competence", and most of us would be way above the proverbial average native speaker in our acquired languages, too.

I know that people get very protective of "bilingual" and "fluent", but I honestly can´t get excited. You either speak the language well enough for your needs and preference or you don´t (so accent is very important for me, but my trilingual grandfather has the thickest Polish accent and couldn´t care less, seems not to be aware of it).

I´ve now lived in Chile a year, and have very little English exposure. Normally no more than 5 hours a week (2 hours staff meeting in English, an hour listening to BBC radio and calls to parents and friends). I don´t read in English apart from essential stuff at work. I write comments on blogs and emails. I often read yours in French, but don´t dare try and write
French any more). I have deliberately avoided English to get as much spanish exposure as I can. In time I´ll do more work on my English, but for now it´s not a priority (and nor will it be next year: I´m going to learn Portuguese as there is the possiblity of working in Brazil in the future).

I´ve noticed
(1) My English spelling has fallen to bits. I suspect spelling ability in English has a lot to do with it being reinforced by reading.
(2) I sometimes struggle to understand spoken English in a way that i don´t with Spanish. I find British English especially hard (I am a native RP speaker). I had to end a call the other day as I was too tired to understand English.

On the Spanish side, my spelling is very good (I had to write all my lectures to start with and so worked a lot on academic written style), I am much more sensitive to accent in Spanish now (though still struggle with the chileans occasionally, but no longer think that that means I can´t speak Spanish: I know a Mexican, a Bolivian and a Paraguayan who have the same problems). I am kinda hoping to find a Spanish speaking house mate next year (hard in this culture where everyone lives with their parents til marriage), and work is giving me more time to study (we had a staff shortage this year so I was thrown in at the deep end).

Interesting, isn´t it, that when we don´t understand something in our second language we tend to think we can´t speak it well, and if we don´t understand in our native language we think that the other person is not speaking it very well.

I agree that there is a significant difference between being fluent in two languages and being bilingual.

My (French) father taught English in a lycée for 45 years, and was fluent in the language. He was a highly accomplished linguist. Like Céline, he "had to make a conscious and concerted effort, over a number of years, to understand the mechanisms of English" but he wasn't bilingual. I am, and fluent in both languages. But I am not a linguist - not a serious one, at any rate.

Céline also mentions the cultural side. This is crucial. Bilinguals are what an African friend of mine once called "des métis cuturels".

Perhaps it can be said that bilingualism is something more or less instinctive, due in most cases to an accident of birth. Many British Asians, for instance, are at least bi -if not tri- lingual. It doesn't make them linguists, of course.

As for the brain staying sharper for longer, encouraging news indeed!