Abnormal: not typical, something out of the ordinary.
Don’t get this word confused with its positive equivalent, exceptional.
If you are abnormal, you are exceptional… in a worrisome sort of way.
Abnormal has an interesting derivation. Ab, of course, means away, or away from. No surprises there. It’s the second half of the word I find most interesting.
In Latin, a carpenter’s square is a norma. A carpenter uses a square to create a line, a standard, or the correct pattern.
To be abnormal, then, is to deviate from the rule, from the standard, from the carpenter’s straight line.