A word about four. It’s cruel to spring such a word on student who are just starting out learning Czech. It’s a sign that they’re really in for some hard work. Sure, three has that Ř in it too, but I think many students figure they can get away with saying “tree,” and they’ll be understood. But four really hits you with all the Czech-ness it can muster: a č right up front, and right next to a t where it shouldn’t be. The y is weird enough, but then we’ve got that ř, and it seems like there’s no hope left!
James Naughton’s Colloquial Czech describes the Czech ř sound like this:
The real Czech specialty here is ř, a single sound which is pronounced like a flatly trilled r with a simultaneous ž/š-like friction.
…which is true, if unhelpful. I think it sounds like a t plus a d plus a ž. Also unhelpful. At the very least, I can tell you this: beginners shouldn’t replace the ř sound with a plain English r, because the sounds are nothing alike. Pronounce it like ž (zh), and you might be better understood, even though they’ll think you have bad pronunciation.
And beginners take heart. Even Czech children have problems with this sound. We’ve all heard about how babies can distinguish all sorts of different vocal sounds that adults may not be able to recognize, and if you don’t grow up hearing Navajo you’ll never understand those subtleties. Well, Czech children (and some adults too) struggle to pronounce the ř correctly. It’s taught and learned like any growing-up skill, rather than being something is picked up naturally like so much of language. We have Czech friends who have a daughter, and they told us the story of the day when she finally learned how to say the ř sound correctly (I think she was three or four years old). She was so excited to tell her father the news, when he came home she ran to him shouting, “Dad, I have a surprise!” And instantly he knew what the surprise was, because the word surprise in Czech is překvapení