Definition: A depression caused by erosion by water or ice. Low-lying land bordered by higher ground; especially elongate, relatively large gently sloping depressions of the Earth's surface, commonly situated between two mountains or between ranges of hills or mountains, and often containing a stream with an outlet.
Definition: A member of the Green Plants clade, including flowering plants, gymnosperms, ferns, clubmosses, hornworts, liverworts, mosses, charophytes, and chlorophytes. http://eol.org/pages/8654492