Excel: Array

An array in Excel is a structure that holds a collection of values. Arrays can be mapped perfectly to ranges in a spreadsheet, which is why they are so important in Excel. An array can be thought of as a row of values, a column of values, or a combination of rows and columns with values. All cell references like A1:A10 and C1:F10 have underlying arrays, though the array structure is invisible in most contexts. All arrays in Excel are wrapped in curly brackets { } and the delimiters between array elements indicate rows and/or columns.  

A comma (,) represents horizontal arrangement in columns, and a semicolon (;) represents vertical arrangement in rows. Since arrays map directly to ranges, all formulas work with arrays in some way, though it isn't always obvious. A simple example is a formula that uses the SUM function to sum the range A1:A10, which contains 10,15,20,25,30,35,40,45,50,55 Inside SUM, the range resolves to an array of values.

An array formula is a formula that can perform multiple calculations on one or more items in an array. You can think of an array as a row or column of values, or a combination of rows and columns of values. Array formulas can return either multiple results, or a single result.