Formulas
- Yang–Mills equations
- Young's inequality for products
- Young tableau
- Kirby calculus
- Kirby–Siebenmann class
- Kirchhoff's theorem
- Kirillov character formula
- Kirillov model
- Kleene fixed-point theorem
- Klein's Encyclopedia of Mathematical Sciences
- Klein four-group
- Klein geometry
- Klein graphs
- Klein quadric
- Kleinian group