re: what's the correct pronunciation of "gyro"?

quote:

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G is silent.

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I've always wondered what purpose silent letters serve.

And how do they decide what letter to use? Like the word pneumatic or opossum, why have a "p" or "o" at the start of those words?

There has to be a logical reason, right? And why use those letters?

Since it's silent, does what letter is used really important? Couldn't a word like "pneumonia" be spelled "fneumonia" or "hneumonia" since the first letter is silent anyway?