【Alone】 , 【Solitary】 , 【Lonely】 , 【Lonesome】 , 【Lone】 , 【Lorn】 , 【Forlorn】 and 【Desolate】 may all refer to situations of being apart from others or emotions experienced while apart.

【Alone】 stresses the fact of physical isolation and also may connote feelings of isolation from others.

• the captain of a ship at sea is a remote, inaccessible creature, something like a prince of a fairy tale, 【alone】 of his kind
  —Conrad

【Solitary】 may indicate a state of being apart that is desired and sought for.

• Netta loved these 【solitary】 interludes . . . . She could dream things there and tell herself stories there, untroubled
  —Powys

It often connotes sadness at the loss or lack of usual or close connections or consciousness of isolation or remoteness.

• being 【solitary】 he could only address himself to the waiter
  —Woolf
• an only child, he was left 【solitary】 by the early death of his mother... whose loss he felt severely
  —Fulton

【Lonely】 may simply indicate the fact of being 【alone】 but more often suggests isolation accompanied by a longing for company.

• he was 【lonely】 , but not in an unhappy sense . . . it was no hardship for him to be 【alone】
  —Canby
• his grim look, his pride, his silence, his wild outbursts of passion, left William 【lonely】 even in his court
  —J. R. Green
• he felt more 【lonely】 and forsaken than at any time since his father’s death
  —Archibald Marshall

【Lonesome】 , often more poignant, suggests sadness after a separation or bereavement.

• you must keep up your spirits, mother, and not be 【lonesome】 because I’m not at home
  —Dickens
• her flight. . . yet smote my 【lonesome】 heart more than all misery
  —Shelley

【Lone】 especially in poetical use may replace either 【lonely】 or 【lonesome】 .

• in his 【lone】 course the shepherd oft will pause
  —Wordsworth
• the mother’s dead and I reckon it’s got no father; it’s a 【lone】 thing
  —George Eliot

【Lorn】 suggests recent separation or bereavement.

• when 【lorn】 lovers sit and droop
  —Praed

【Forlorn】 indicates dejection, woe, and listlessness at separation from someone dear.

• as 【forlorn】 and stupefied as I was when my husband’s spirit flew away
  —Hardy
• as 【forlorn】 as King Lear at the end of his days
  —G. W. Johnson

【Desolate】 is most extreme in suggesting inconsolable grief at loss or bereavement.

• fatherless, a 【desolate】 orphan
  —Coleridge
• for her false mate has fled and left her 【desolate】
  —Shelley

【Solitary】 , 【lonely】 , 【lonesome】 , 【desolate】 are applied to places and locations more than the other words discriminated above. 【Solitary】 may be applied either to something that is apart from things similar or that is uninhabited or unvisited by human beings.

• a 【solitary】 chamber, or rather cell, at the top of the house, and separated from all the other apartments by a gallery and staircase
  —M.W. Shelley

【Lonely】 may be applied to what is either far apart from things similar and seldom visited or to what is inhabited by only one person or group and conducive to loneliness.

• heard not only in the towns but even in 【lonely】 farmhouses
  —Anderson

【Lonesome】 has much the same suggestion.

• like one that on a 【lonesome】 road doth walk in fear and dread
  —Coleridge

【Desolate】 indicates either that a place is abandoned by people or that it is so barren and wild as never to have attracted them.

• as if nothing had life by day, in that lifeless 【desolate】 spot
  —Trollope