Quick answer
Vicious means cruel, violent or savage. Viscous means thick and slow-flowing — honey is viscous. The words differ by two letters and mean nothing alike; "a viscous attack" describes a slow-moving syrup rather than a brutal one.
The core difference
Cruelty and thickness.
- vicious — cruel, savage: a vicious assault, a vicious rumour.
- viscous — thick, resistant to flowing: a viscous liquid.
The roots
Vicious is from Latin vitium, fault or vice — originally meaning full of vice, later cruel. Viscous is from viscum, mistletoe, whose berries produce a sticky substance used to make birdlime. So the thickness word is named after glue made from mistletoe.
The related terms
Viscosity is the measure of a fluid's resistance to flow. Vicious circle takes the cruelty spelling — a self-reinforcing bad situation.
Frequently asked questions
Which one means thick?
Viscous. Vicious means cruel or violent.
Is it "vicious circle" or "viscous circle"?
Vicious circle — a self-reinforcing harmful situation.
Where does viscous come from?
Latin viscum, mistletoe — whose sticky berries were used to make birdlime.
