Students often use the expression “ça va” as an adjective. I’ve heard, for example, “Le film était ça va,” to mean the film was “OK.” A French person would have no clue what that sentence meant.
“Ça va” means “it’s OK,” in the sense that things are going well, but it is a sentence unto itself rather than an adjective.
If you need an adjective, “acceptable” would do or “médiocre.”
To incorporate “OK” in a sentence, you would need the appropriate tense of “aller” and, most likely, since it’s informal, the subject “ça” with no other verb. For example, in response to the question, “How was the film yesterday?” one could say “Ça allait,” meaning “it was OK.” If someone is worried about the future, a friend could respond reassuringly that “Ça ira” in the future.
Back Bay Français 
In response to the question “how was the film yesterday?” for “OK” could you say “comme si comme ça” – doesn’t that mean ok too? Or not really – I wondered…
Actually, sometimes I hear french people use the english word “OK” but it’s usually more just as a passing filler expression, like “Bon! OK. On y va” not as in “Le film était OK.”
But on another note with the expression “Ça va” – here, when you greet your friends who you say “tu” to, everyone says “ça va?” / “oui ça va!” but even people who say “Vous” to me, will often greet with a “ça va?”. This confuses me… For example, when I go to a brasserie or to the marché in my quartier, the waiter or vendor greets with a “Bonjour Madame, ça va?” but then says “Voulez vous boire quelques choses?” or “vous voulez des olives?” and then will “vous” me from then on. I do not hear “Comment-allez vous” that much (something I was taught to use). This inital “ça va?” throws me off as I thought that might set the tone for whether or not we vous or tu (something very confusing to me!!)
This is a little unrelated but another thing I never heard before I moved here is as follows: In shops when you buy something you say “Merci” or “Merci beaucoup” and the person responds simply “C’est moi.” Very, very common!!! Do you know what this is short for?? or how it started?
Thank you.. bonne journée!
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Yes, “comme-ci comme ça,” meaning ‘so-so’ would work to describe something like a film. But I wasn’t correcting “le film était ok” but rather “Le film était ça va.” Was that clear? The former doesn’t sound very French but the latter has no meaning.
En principe, yes, “Ça va” does set an informal tone and the French are definitely getting more and more informal. The contrast between that and the use of “vous” would seem to indicate less formality but no less respect.
Parisians, and especially waiters and vendors, are known for being rushed and, you have to admit, “Ça va” sure does take less time than “Comment allez-vous?” Two whole syllables!
The “C’est moi” response you get in Parisian shops in response to your “Merci” would imply “C’est moi qui vous remercie.”
Make sense?
Susan
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