Formulas
- Kadison–Kastler metric
- Kadison–Singer problem
- Kadomtsev–Petviashvili equation
- Kakeya set
- Kakutani's theorem (measure theory)
- Kampé de Fériet function
- Milnor–Thurston kneading theory
- Kan-Thurston theorem
- Milnor–Wood inequality
- Kan extension
- Near-field (mathematics)
- Nilpotent
- Kantorovich inequality
- Kaprekar number
- Orthogonal functions