Insomnia is an experience of inadequate or poor quality sleep as characterized by one or more of the following sleep complaints: difficulty initiating sleep; difficulty maintaining sleep; waking too early in the morning.
MoreLink: http://www.sleepfoundation.org/site/c.huIXKjM0IxF/b.2421129/k.251A/Cant_Sleep_Learn_about_Insomnia.htm=m