Quote Originally Posted by radomir View Post
Really there is no additional rule for helping where в or б; и or ы must be used apart from this last case for г. х. ж ?
The question is strange. What is a spelling rule? It is a rule which explains how to SPELL a word in case when you cannot detect it from the pronunciation. I.e. if there are some letters which are pronounced the same, you need a spelling rule for them. For example, in English "cat" and "kite" the initial consonant is the same. Or in English "late" and "wait" the vowel sound is the same.

As to "в" and "б", they are two distinct sounds in Russian, and no one is expected to confuse them. So, they are spelt just the way they are pronounced: compare "ваза" and "база". The same is true for "и" and "ы": they are two distinct vowels, e.g.: "бил" and "был" - each word is spelt just as it is pronounced.

The only exception is you have to learn that you never write "ы" after "ж" and "ш", you should write "и" instead. But in pronunciation, there is always "ы" after those consonants: we write "шил, жир", but we pronounce "шыл, жыр" etc.

And one more thing: we also pronounce only "ы" after "ц", but some words are spelt with "ы" and others are spelt with "и", e.g.: цыган (pronounced "цыган"), but цирк (pronounced "цырк"), you just have to memorize it.

In all other cases, it is just phonetic.