A heterocycle is an organic compound whose carbon ring contains one or more heteroatoms ($ O $, $ S $, $ N $ ...)
The body of the name refers to (in order of precedence!) the heteroatoms:
The suffix denotes the ring size:
The order $ O \gt S \gt N $ is for the body of the name and the numbering!
If the cycle contains the maximum possible double bonds (completely unsaturated), hydrogen attached to an atom bound by two single bonds should be indicated with the prefix H
1- H -azirine
2- H -azirine
If the cycle does not contain the maximum possible double bonds, the hydrogen atoms attached to two ring atoms bound by single bonds are indicated by the prefixes dihydro , trihydro ... The rest of the name is the name of the cycle with the maximum possible double bonds.
In the case of simple molecules the traditional names are preferred:
See → here:
→ Bicyclic compounds → Bicycloalkanes: exercises → Spiranes: exercises → Current heterocycles → Current nitrogen heterocycles → Common oxygenated and sulphurized heterocycles → Systematic nomenclature (Hantzsch-Widman) of simple heterocycles → Systematic nomenclature (Hantzsch-Widman) of condensed heterocycles → Nomenclature of substituted simple heterocycles → Nomenclature of substituted condensed heterocycles