Darkness: it is in reality the total absence of light. A dark place has, if at all, few sources of light present, making everything difficult to see, as in the night. Alternating exposure to light and darkness (day and night) has caused a great variety of evolutionary adaptations to darkness.
Darkness can also mean the presence of shadows, evil, or depression.
Darkness can have a strong psychological impact. It can cause depression in people suffering from seasonal depressive disorder (or winter depression), fear in people suffering from nictofobia.