Definition
Array
An array arranges objects in equal rows and equal columns so the total can be counted or multiplied.
What it means
Think of neatly lined-up cinema seats. Every row has the same number of seats, and the seats also line up in columns. That neat structure lets you count by equal groups instead of one by one. A 3-by-4 array has 3 rows of 4, so it shows 3 × 4. Looking the other way, it has 4 columns of 3, so it also shows 4 × 3.
Remember it
Picture neat cinema seats: every row lines up with every column.
Example
Twelve counters are placed in 3 equal rows with 4 counters in each row. The array shows 3 × 4 = 12. It also has 4 columns of 3 counters, so 4 × 3 = 12 describes the same total.
Watch for
A scattered group, or rows with different numbers of objects, is not a rectangular array.
Common mix-up
The number of rows or columns is not the total. Multiply the two counts to find how many objects there are altogether.
Exact meaning
A rectangular array is an arrangement of objects in aligned rows and columns, with the same number of objects in each row and the same number in each column. The row count and column count are factors; their product is the total number of objects.