An arrangement of objects in rows and columns. All the rows have the same number of objects. All the columns have the same number of objects.

In an array, a line of objects that goes up and down.

A number that can be split into 2 equal-size groups or made into pairs without any objects left over.

A number is odd if that number of objects cannot be split into two equal groups or made into pairs without any objects left over.

In an array, a line of objects that goes side to side.