Aperture priority
From The Glossary of Digital Photography
A setting on an automatic camera that enables the photographer to select the aperture; the camera then selects the shutter speed. This method is used when the photographer wants to control depth of field for creative effect, either by having a large depth of field, so that most things are in focus, or a shallow one, where only one or a few things are in focus. When using this setting, watch the shutter speed and make sure to use a tripod or other support when necessary. Some cameras, if hand-held, will not warn the photographer when the shutter speed is so slow that the image is likely to be blurred.
