The term 'by oneself' can be expressed in a variety of ways, including SOLO (4 letters), STAG (4 letters), ALONE (5 letters), UNAIDED (7 letters), LONE (4 letters), FORLORN (7 letters), ALLALONE (8 letters), UNRIVALED (9 letters), UNASSISTED (10 letters), and SINGLEHANDED (12 letters). These words all describe the same concept: being without help or companionship. This could mean being ALONE in a physical sense, or it could refer to a task that is completed without assistance.