When to pronounce “s” at the end?

Question

For instance, "vous" has a silent "s", unless it's something like "Je vous ai vu." (I'm not sure that I constructed that properly, but you get the point-- the "s" is pronounced in that case.)

But what if you have "Je voudrais acheter un billet." ? Is it "voo-drez"?

Basically, I'm asking do you always pronounce it if the next word begins with a vowel, or only under certain circumstances?

Answer 1

A general rule: use whatever is the easiest to pronounce.

In the case of “Je vous ai vu”, I hope you will find [ʒə.vu.z‿e.vy] easier than [ʒə.vu.e.vy], because you would hardly be understood if you omit the liasion.

In “Je voudrais acheter un billet” it doesn't matter much. Personally I use a very light liaison (something between a /z/ and an aspirated /h/).

You will find more information on the Liaison (French) articles on Wikipedia.

Answer 2

I would say that usually when you have a s (or x) before a vowel, you can make the liaison. This is in order to avoid hiatuses. Usually, it's intended to be easier to pronounce. But if you don't do it, you still will be completely understandable don't worry for that.

edit:

Full official rules from l'Académie française here. There are mandatory liaisons, forbidden ones, and optional cases (if you do the liaison then, it would be considered as 'un parlé soutenu', more or less the equivalent of the 'formal' register in english)

(other link that may help - in French of course: here, or this one - in english)

A quite commom mistake on the liaison (confusion between a 't' and a 's' of sometimes a 'n' sound) is called 'pataquès'.