Senegal: noun: Senegalese (singular and plural)

adjective: Senegalese

Seychelles: noun: Seychellois (singular and plural)

adjective: Seychelles

Sierra Leone: noun: Sierra Leonean(s)

adjective: Sierra Leonean

Singapore: noun: Singaporean(s)

adjective: Singapore

Slovakia: noun: Slovak(s)

adjective: Slovak