Use arrays (or equivalent) in the design of solutions to simple problems
An array is a collection of data items of the same data type. Each item can be accessed directly via it's index (position in the array).
Array access is very fast as each element can be accessed directly.
A multi-dimensional array is an array with more than one dimension. Think of it as a series of arrays inside of eachother.
An n-dimensional array can be represented mathematically as an n-dimensional matrix.
A multi-dimensional array may be used when representing a matrix.
A one-dimensional array is a useful way of representing a vector. A two-dimensional array is a useful way of representing a matrix. More generally, an n-dimensional array is a set of elements with the same data type that are indexed by a tuple of n integers, where a tuple is an ordered list of elements.