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Plain Jane usually refers either to a woman who simply is of average or plain appearance. The term is thought to have spawned from character Jane Eyre in popular Victorian author Charlotte Bront's Jane Eyre. References
In geography, a plain is land with relatively low relief, that is flat or gently rolling. Prairies and steppes are types of plains, and the archetype for a plain is often thought of as a grassland, but plains in their natural state may also be covered in shrublands, woodland and forest, or vegetation may be absent in the case of sandy or stony plains in hot deserts. The Walachian plain is known for his thick deposits of loess and its fertile black earth
Coastal plain, an area of low-lying land adjacent to a sea; The difference between a floodplain and an alluvial plain is that the floodplain represents the area experiencing flooding fairly regularly in the present or recently, whereas an alluvial plain includes areas where the floodplain is now and used to be, or areas which only experience flooding a few times a century.