The adj alone has 4 senses (first 3 from tagged texts)
1. (26) alone -- (isolated from others; "could be alone in a crowded room"; "was alone with her thoughts"; "I want to be alone")
2. (4) alone, lone, lonely, solitary -- (lacking companions or companionship; "he was alone when we met him"; "she is alone much of the time"; "the lone skier on the mountain"; "a lonely fisherman stood on a tuft of gravel"; "a lonely soul"; "a solitary traveler")
3. (1) alone, only -- (exclusive of anyone or anything else; "she alone believed him"; "cannot live by bread alone"; "I'll have this car and this car only")
4. alone, unique, unequaled, unequalled, unparalleled -- (radically distinctive and without equal; "he is alone in the field of microbiology"; "this theory is altogether alone in its penetration of the problem"; "Bach was unique in his handling of counterpoint"; "craftsmen whose skill is unequaled"; "unparalleled athletic ability"; "a breakdown of law unparalleled in our history")
Overview of adv alone
The adv alone has 2 senses (first 2 from tagged texts)
1. (32) entirely, exclusively, solely, alone, only -- (without any others being included or involved; "was entirely to blame"; "a school devoted entirely to the needs of problem children"; "he works for Mr. Smith exclusively"; "did it solely for money"; "the burden of proof rests on the prosecution alone"; "a privilege granted only to him")
2. (28) alone, solo, unaccompanied -- (without anybody else; "the child stayed home alone"; "he flew solo")