AISLE

The Aisle is a lateral or longitudinal divisions of a church, separated from the nave (sometimes called the centre aisle) by rows of piers, pillars, or columns. The term is popularly used to describe the passage between pews or seating. Sometimes a church has one side-aisle only. Often the aisle is continued around the apse. Occasionally the aisles stop at the transepts. The aisle is generally one story, but occasionally there is an upper story, sometimes used as a gallery. As a general rule, churches are divided into three aisles, but there is no fixed rule that governs the number.

Picture taken from : http://www.businessinsider.com/movement-to-tax-church-gains-momentum-2012-9

Acknowledgement: http://www.newadvent.org/cathen/01237c.htm