SF

Noun

• Initialism of science fiction or speculative fiction, often used to avoid having to choose between the two.
• Initialism of square feet
• Initialism of small forward
• Abbreviation of semifinal

Proper Noun

• Initialism of San Francisco
• Initialism of Sinn Fein, an Irish political party
• Initialism of Suomi–Finland, former country code for Finland
• Initialism of {{w}}
• Initialism of w:en:Super Formula Championship

Adjective

• Initialism of smoker-friendly: not objecting to people who smoke tobacco