A matrix with `` m '' rows and `` n '' columns is called an `` m '' × `` n '' matrix or `` m '' - by - `` n '' matrix , while `` m '' and `` n '' are called its `` dimensions '' .
A matrix with `` m '' rows and `` n '' columns is called an `` m '' - by - `` n '' matrix ( or `` m '' × `` n '' matrix ) and `` m '' and `` n '' are called its dimensions .