
Loner
Often Negative
The term 'loner' can imply someone is lonely or anti-social, which might be viewed negatively. 
Voluntary Solitude
'Loner' often means choosing to be alone, not just being alone by circumstance. 
Not a Hermit
Don't confuse 'loner' with 'hermit'. Loners can have social contact but prefer solitude at times. 