[Al-Khwarizmi]

Spanish also has that property, i.e. given a word (existing or invented), there is a single way to pronounce it, easy to determine following some rules.*

Finnish (from what I've heard, as I don't speak it) is even more regular in the sense that this also works the other way around, i.e., if you hear a word, you can use rules to know how to spell it. This does not always hold in Spanish (e.g. B and V are pronounced the same, so you cannot know if you're hearing "vaca" or "baca" without resorting to context and common sense reasoning) although it does hold for all but a small bunch of grapheme pairs.

* Modulo regional variants, but if you focus in any given variant (e.g. Spanish from Spain) this holds.

[z500]

The only problem with that is the vast number of declensions. Sure they're not as wildly divergent as, say Latin or Ancient Greek, and there's no gender, but because of all the cases there's a lot of subtle variations to remember

[Koshkin]

Sure; this has nothing to do with the way written words are spoken, though.

[umanwizard]

Spanish does have a few exceptions, mainly due to loanwords from indigenous American languages. For example, it would not be possible to guess that the X in México is pronounced like Spanish J.

[ivm]

México is because of the old orthography, before it was Don Quixote too.

[Koshkin]

You do not guess, you learn.

[throwaway894345]

I agree, and I've heard this property referred to by linguists as a "shallow orthography".

[Koshkin]

> a single way to pronounce it

Within a particular dialect, that is.