A symmetrical fold is a fold that shows a mirror image on both sides of the axial plane while an asymmetrical fold doesn't have a mirror image. An overturned fold occurs when the axial plane is tilted and the beds may dip in the same direction on both sides of the axial plane. An extreme example of an overturned fold happens when the axial plane is horizontal and is called a recumbent fold. Monocline is a special kind of fold with only one limb. This can happen when sedimentary rocks sag over an underlying fault.
Domes are circular or elliptical anticline resembling an inverted bowls.
Sedimentary layering dips away from the center of a dome in all directions. Basins are similar to domes. They are syncline folds where the layering dips toward the center of the basin. Domes and basins can be small structures only a few kilometers in diameter but are often much larger. They result from regional warping of the entire continental crust.