How many times was I told "my son / daughter is fluent" by proud mums and dads at Parents' Evenings when I was a languages teacher back in the day?
These children certainly were NOT fluent as they were only doing CSE / O-level / GCSE at the time.
[Lingoland]
Fluent
So what does fluent mean? Literally "flowing" or "fluid".
As far as I'm concerned I only became fluent
- when I stopped translating in my head;
- when I began to think, and even dream, in Spanish;
- when I could swear successfully and accurately in Spanish;
- when my interlocutors complimented me on my fluency.

[Vidalingua]
The same applies to my German, but not to my French, which is only to A-level standard.
Footnote:
When I graduated 53 years ago I was fluent and met all the above-listed criteria with the exception of the one about swearing.
That took a few years of visits, extended stays and embarrassing moments in Spain and Germany to get right.
Now, after 18 years of living here I've got it cracked and can curse like the best of them!
[Amazon]
Interesting Links:
False friends in Spanish and English
Masculine or feminine?
"Roses are red, violets are blue ....."
Spanish spelling and pronunciation
Top 10 Tips for Learning Spanish
¿TÚ or USTED?
© Don Pablo
Pictures:
Amazon, Lingoland, Vidalingua
Thanks:
Paul Whitelock
Tags:
A-level, Amazon, CSE, curse, Don Pablo, flowing fluency, fluent, fluid, French, GCSE, German, Lingoland, O-level, Paul Whitelock, Spanish, swear, Vidalingua