What is the slant height of a rectangular or square pyramid?

An edge of a triangle face
The height of a pyramid from the Apex straight down to the middle of the base of the pyramid
The distance across the triangle face
The height of the Apex straight down to the base of the triangle face where it forms a right angle

The slant height of a rectangular or square pyramid is the distance across the triangle face, from the Apex straight down to the middle of the base of the pyramid.