What is the intersection operator for?

To read a cell at the crossing of two named ranges, for example =January Sales. It is rare; in most formulas, the space is a typo.

The #NULL! error

The rarest of the errors, and almost always a typo: a space where a comma or a colon was needed.

What it means

For Excel, a space between two ranges is an operator: the intersection. =SUM(A1:A5 C1:C5) asks for the sum of the cells the two ranges share; there are none, hence #NULL!.

Where it comes from

A space instead of a comma: =SUM(A1 B1) instead of =SUM(A1,B1).
A space instead of a colon: =SUM(A1 A10) instead of =SUM(A1:A10).

Fixing it

Replace the space with , (several ranges) or : (one range from A1 to A10).

Tools that help

Explain a formula: shows the intersection where a list was expected.

Frequently asked questions

What is the intersection operator for?: To read a cell at the crossing of two named ranges, for example =January Sales. It is rare; in most formulas, the space is a typo.