Aid climbing—A type of climbing that makes use of rope, fixed bolts, pitons or foot slings, rather than features on the rock itself, to ascend the face. Opposite of free climbing.

An arête is a vertical corner of rock pointing out, away from the main cliff mass. Also called an “outside corner.” The opposite of an arête is a dihedral. Stemming up a chimney route.

When rock climbers rappel, they lower themselves down the side of a wall or mountain. To rappel safely, a climber uses special anchors and climbing ropes, as well as the help of another person.

Headwall: The upper section of a mountain where the terrain is set off from the terrain below by being more steep.