Abnormal means different from what is usual, in a worrying way. An abnormal result, abnormally high, abnormal behaviour.
In medicine it means outside the reference range, which is defined so that a small share of perfectly healthy people fall outside it — so an abnormal result on its own means very little. Applied to a person it is a heavy word and mostly avoided now.
1adjectiveabnormalDifferent from what is usual, in a worrying way.
“The doctor noticed an abnormal heartbeat and ordered more tests.”
abnormal is a quality of difference.
From ab-, away from, plus normal, from Latin norma, a carpenter's square. The earlier form was anormal.
Ancient Greek
ἀνώμαλος
Latin
abnormis — departing from normal
English, today
abnormal
From ab- + normal. From ab- + normal. First attested in 1835, replacing the earlier anormal and even earlier abnormous, from Latin abnormis (“departing from normal”), from either ab- + norma, or Ancient Greek ἀνώμαλος.
Etymology from Wiktionary, CC BY-SA