without companions; lone; characterised by aloneness; solitary; dejected by the awareness of being alone; a complex and usually unpleasant emotional response to isolation. Loneliness typically includes anxious feelings about a lack of connectedness or communality with other beings, both in the present and extending into the future. As such, loneliness can be felt even when surrounded by other people. The causes of loneliness are varied and include social, mental, emotional, and spiritual factors.
Loneliness has also been described as social pain — a psychological mechanism meant to alert an individual of isolation and motivate him/her to seek social connections.
Etymology: Middle English; aphetic variation of alone, used attributively.