Postby ColdSteel » Jan 27th, 14, 16:48
Generally, there is no a big difference between these words, when you pronounsing them. Both sound like "эта". Maybe sometimes the letter "о" in the word "это" sounds close to the English sound "e" in words with "-er" ending.
Yes, in some regions of Russia it is a local standard of pronunciation, when the letter "о" always sounds like "о" and never like "а". They may be regions that close to Ukraine, or some little towns, villages, mainly in the Volga Region (Поволжье).
The main rule is to pronounce the letter "о" like "о", when it is under a stress only, and like "а" - without stress.
это - [эта] - this (neuter), it
эта - [эта] - this (feminine)
молоко - [малако] - a milk
хорошо - [харашо] - good, that's good
хороший - [харошый] - a good one (masculine)
копыто [капыта] - a hoof (single, neuter)
копыта [капыта] - hooves (plural, neuter)
As you can see, the last two words sound the same.