Array form

-          Return the value of a specified cell or array of cells

Reference form

-          Return a reference to specified cells

Array form

Syntax

INDEX(array,row_num,column_num) 

Array - is a range of cells or an array constant. 

-          If array contains only one row or column, the corresponding row_num or column_num argument is optional.

-          If array has more than one row and more than one column, and only row_num or column_num is used, INDEX returns an array of the entire row or column in array. 

Row_num - selects the row in array from which to return a value. If row_num is omitted, column_num is required. 

Column_num - selects the column in array from which to return a value. If column_num is omitted, row_num is required.         

Reference form

Syntax

INDEX(reference,row_num,column_num,area_num) 

Reference - is a reference to one or more cell ranges. 

-          If you are entering a nonadjacent range for the reference, enclose reference in parentheses.

-          If each area in reference contains only one row or column, the row_num or column_num argument, respectively, is optional. For example, for a single row reference, use INDEX(reference,,column_num). 

Row_num - is the number of the row in reference from which to return a reference. 

Column_num - is the number of the column in reference from which to return a reference. 

Area_num  - selects a range in reference from which to return the intersection of row_num and column_num. The first area selected or entered is numbered 1, the second is 2, and so on. If area_num is omitted, INDEX uses area 1.