absent-mindedly
Word family
Synonym discussion
Sense: adverb/1
All four describe acting without full mental presence, but the cause and feel differ. 'Absent-mindedly' suggests the mind has drifted off to its own thoughts, often habitually, with a slightly affectionate or harmless tone (Yan stirring her tea while staring at the rain). 'Distractedly' points to a specific outside thing pulling attention away — a phone buzzing, a worry, a noise — and often feels more momentary and stressed. 'Vacantly' describes the look or manner more than the thought: the eyes are empty, and there may be no particular thought at all (he stared vacantly at the wall). 'Inattentively' is the most neutral and formal, often used in reports or feedback ('the driver was behaving inattentively'), and carries a hint of fault.
Etymology
Built from the adjective 'absent-minded' (1810s) plus the adverb suffix '-ly'. 'Absent-minded' itself joins 'absent' (from Latin 'absentem', meaning 'being away') with 'minded' (having one's mind in a particular state), so the literal idea is 'with one's mind being away'. The whole word captures the picture of the body being present while the thoughts are somewhere else.