| − | Since sleep is a fairly basic, but abstract, concept, the morphology of the corresponding word is useful in historical [[linguistics]] for determining fine relationships between related languages. The [[noun]] ''sleep'' and its derived [[verb]] and [[adjective]] forms ''to sleep, sleepy'' in English both originate from a common Germanic root *SLAEP, as exemplified by the many cognates of the word in other Germanic languages such as the Dutch ''slap, slapen, slaeperig'' and the German ''Schlaf, schlafen, schläflig.'' | + | Since sleep is a fairly basic, but abstract, concept, the morphology of the corresponding word is useful in historical [[linguistics]] for determining fine relationships between related languages. The [[noun]] ''sleep'' and its derived [[verb]] and [[adjective]] forms ''to sleep, sleepy'' in English both originate from a common Germanic root *SLAEP, as exemplified by the many cognates of the word in other Germanic languages such as the Dutch ''slap, slapen, slaeperig'' and the German ''Schlaf, schlafen.'' |