Extension theorem

• Carathéodory's extension theorem
• Hartogs' extension theorem
• Isomorphism extension theorem
• Kolmogorov extension theorem
• Krein extension theorem
• M. Riesz extension theorem
• Ohsawa–Takegoshi L2 extension theorem
• Szpilrajn extension theorem
• Tietze extension theorem
• Urysohn extension theorem
• Whitney extension theorem