word | | Country name |
| conventional | Serbia | conventional long form: Republic of Serbia conventional short form: Serbia local long form: Republika Srbija local short form: Srbija former: People's Republic of Serbia, Socialist Republic of Serbia |
| conventional | Seychelles | conventional long form: Republic of Seychelles conventional short form: Seychelles local long form: Republic of Seychelles local short form: Seychelles |
| conventional | Sierra Leone | conventional long form: Republic of Sierra Leone conventional short form: Sierra Leone local long form: Republic of Sierra Leone local short form: Sierra Leone |
| conventional | Singapore | conventional long form: Republic of Singapore conventional short form: Singapore local long form: Republic of Singapore local short form: Singapore |
| conventional | Slovakia | conventional long form: Slovak Republic conventional short form: Slovakia local long form: Slovenska Republika local short form: Slovensko |
| conventional | Slovenia | conventional long form: Republic of Slovenia conventional short form: Slovenia local long form: Republika Slovenija local short form: Slovenija former: People's Republic of Slovenia, Socialist Republic of Slovenia |
| conventional | Solomon Islands | conventional long form: none conventional short form: Solomon Islands local long form: none local short form: Solomon Islands former: British Solomon Islands |
| conventional | Somalia | conventional long form: none conventional short form: Somalia local long form: Jamhuuriyada Demuqraadiga Soomaaliyeed local short form: Soomaaliya former: Somali Republic, Somali Democratic Republic |
| conventional | South Africa | conventional long form: Republic of South Africa conventional short form: South Africa former: Union of South Africa abbreviation: RSA |
| conventional | South Georgia and the South Sandwich Islands | conventional long form: South Georgia and the South Sandwich Islands conventional short form: South Georgia and South Sandwich Islands abbreviation: SGSSI |
| conventional | South Sudan | conventional long form: Republic of South Sudan conventional short form: South Sudan |