The letter "ayin" is a silent letter which changes the way a word is pronounced
If you want to see some freaky stuff, try learning one of the Celtic languages where they do mutation - so in Gaidhlig, a word that starts with an m (like 'mor' - big) has, under certain circumstances, an 'h' put after it. This, as one might expect, changes the sound. So "very big" (gle mhor) is pronounced as "gle vor".
There are reasonable simple rules about how this happems (starting letter == b,f,m,p and mumble mumble) but it catches out the beginner.
And don't get me started on balanced thick and thin vowels. No really, don't - I can't remember the rules..
I'm sure that Welsh, Cornish and Breton have similar-but-different mutation rules (so Cymru becomes Gymru etc etc) but I know even less about that branch of Celtic languages.
 It was 20 years ago that we learnt a bit of Scots Gaidhlig and my brain has had to process a lot of alcohol^W stuff since then.