¹alone

alone, solitary, lonely, lonesome, lone, forlorn, desolate mean isolated from others. alone stresses the objective fact of being by oneself with slighter notion of emotional involvement than most of the remaining terms <everyone needs to be alone sometimes>. solitary may indicate isolation as a chosen course <glorying in the calm of her solitary life> but more often it suggests sadness and a sense of loss <left solitary by the death of his wife>. lonely adds to solitary a suggestion of longing for companionship <felt lonely and forsaken>. lonesome heightens the suggestion of sadness and poignancy <an only child often leads a lonesome life>. lone may replace lonely or lonesome but typically is as objective as alone <a lone robin pecking at the lawn>. forlorn stresses dejection, woe, and listlessness at separation from one held dear <a forlorn lost child>. desolate implies inconsolable grief at loss or bereavement <desolate after her brother's death>.

alone, solitary, and lonely mean separated from others. alone is used when a person is entirely without company. <I was left alone in the room.> solitary may be used to emphasize the fact of being the only one. <The old tree had but a solitary apple.> lonely is used when someone longs for company. <I felt lonely after my friends left.>

Take away letters from the beginning of alone, and you'll find related words. If you are alone you are separate from others, or the lone person to do something, or the only one.