alone/lonely
 

alone, lonely, lonesome and lone
Alone means 'without others around'. Lonely (and informal ArnE lonesome)
means 'alone and unhappy because of it'. Compare:
I like to be alone for short periods.
But after a few days I start getting lonely lonesome.
Alone can be emphasized by all.
After her husband died, she was all alone.
Alone is not used before a noun (see 12.3). Lone and solitary can be used
instead; lone is rather literary.
The only green thing was a lone/solitary pine tree.