To add to sidster, I think in addtion to the raswa and dhirga, there is one more difference between 'Reason' and 'Region'. That is the pronouncition of  "ज". reason = reezan and region =rijan. There should be difference between 'zone' and 'jone'. Both are not the same 'ज'.This can't be explained in written for as I said earlier, but it has high importnce in the texture of our speech.