For an m×nm\times n AA, its transpose ATA^{\mathsf T} is the n×mn\times m matrix defined by

(AT)ij=Aji.(A^{\mathsf T})_{ij}=A_{ji}.

Transposition interchanges rows and columns and satisfies (AT)T=A(A^{\mathsf T})^{\mathsf T}=A.

Algebraic identities

Over a commutative field, (AB)T=BTAT(AB)^{\mathsf T}=B^{\mathsf T}A^{\mathsf T}, (A+B)T=AT+BT(A+B)^{\mathsf T}=A^{\mathsf T}+B^{\mathsf T}, and (cA)T=cAT(cA)^{\mathsf T}=cA^{\mathsf T}, whenever the operations have compatible sizes.

For complex matrices, the transpose does not conjugate entries. The conjugate transpose is A=ATA^*=\overline A^{\mathsf T}; these two operations agree for real matrices.