Wythe of brick

In the photo below, you can see a double-wythe brick wall cut right down the middle. So, what is a wythe?

Wictionary.com says

EtymologyEdit

Middle English from Old English withthe(withe)

A wythe of brick is a single vertical assembly of units.  In this case, and typical with above grade exterior or even interior demising walls in Capitol Hill the wall is a double wythe.

You can see a perfect cross-section of the bedding mortar and stretcher mortar between bricks.  The vertical joint between wythes is called the collar joint.

A wall cut in section straight through shows the collar bond, in this case a weak connection of a running bond

A wall cut in section straight through shows the collar bond, in this case a weak connection of a running bond