How do i know if im depressed. is there a normal feeling sad all the time or do u draw the line and label it depression?

Length and intensity: We all feel sad at some times in our lives but we usually get over it .Pathological sadness or depression lasts for several weeks associated with loss of interest in daily activities, insomnia or hypersomnia, crying spells, sometimes patients claim that they ares depressed they can't even cry, loss of energy, memory impairment , passive wishes to die or even suicidal ideation.