Re dialects or types of-0 dialects is actually from style of-0 grammars. It indicates TM can circle forever into strings which are perhaps not a part of the language. Re also languages are also known as Turing identifiable dialects.
A recursive language (subset of RE) can be decided by Turing machine which means it will enter into final state for the strings of language and rejecting state for the strings which are not part of the language. e.g.; L= is recursive because we can construct a turing machine which will move to final state if the string is of the form a n b n c n else move to non-final state. So the TM will always halt in this case. REC languages are also called as Turing decidable languages.
- Union: When the L1 while L2 are two recursive dialects, their commitment L1?L2 will additionally be recursive because if TM halts having L1 and you will halts getting L2, it will halt having L1?L2.