| Category | Keyword | API Naming Convention |
| UChar, Unicode and Message Formatting | u | u_<function name> |
| UResourceBundle | ures | ures_<function name> |
| ULocale | uloc | uloc_<function name> |
| UConverter | ucnv | ucnv_<function name> |
| UCollator | ucol | ucol_<function name> |
| UNumberFormat | unum | unum_<function name> |
| UDateFormat | udat | udat_<function name> |
| UCalendar | ucal | ucal_<function name> |
| UBreakIterator | ubrk | ubrk_<function name> |
| Constants | u<keyword>_<constant name> | |
| Acquiring an International Service | u<keyword>_open u<keyword>_openRules |
|
| Releasing the Acquired International Service | u<keyword>_close | |
| Methods | u<keyword>_<method name> |