Let X {\displaystyle {}X} denote a scheme and let F {\displaystyle {}{\mathcal {F}}} and G {\displaystyle {}{\mathcal {G}}} denote two locally free sheaves (of rank r {\displaystyle {}r} and s {\displaystyle {}s} ) together with a surjective sheaf homomorphism
Then the kernel sheaf kern ψ {\displaystyle {}\operatorname {kern} \psi } is also locally free (of rank r − s {\displaystyle r-s} ).