[jessriedel]

"X ~ p(x)" means "X is a random variable drawn from the probability distribution p(x)" or maybe "X is drawn from p(x)" for short.

Are you sure it's a matter of knowing what to say (in your head) vs knowing the definition of the notation in the first place? I am pretty familiar with this notation, but I rarely verbalize it mentally. I can tell because I read and understand it quickly without problem, but on the rare occasion when I have to read it aloud I realize I'm not sure how I should pronounce it.

[spinningslate]

Thanks for the explanation.

Agree it's more "say in my head" than "speak out loud". But I still need to know what to say - internally or externally. Without knowing that ~ denotes "drawn from", all I can say is "X tilde p of x". That has no semantics; no intuition. Whereas knowing that $\in$ means "is a member of", I can read "x \in X" as "x is a member of X".

> but I rarely verbalize it mentally

Neither do I when I know something well. For example, I don't explicitly verbalise "is a member of" now, even internally. There's a shortcut hard-wired in that understands it without needing to pronounce it explicitly. In fact that short cut goes beyond the syntax: it goes straight to the intuition of "x represents any member of the set X". But I had to go through the process of saying it on the way to the shortcut.

[jessriedel]

OK, but if you know the formal definition, and you're not reading it out loud, why not just make something up? I actually don't know whether "is drawn from" is the "correct" way to pronounce the tilde. I think maybe other people say "is distributed as".