Prescribe means to lay down as a rule or order officially — a doctor prescribes medicine, a regulation prescribes a procedure. Proscribe means to forbid or condemn. They are near-opposites separated by one letter, which makes the swap unusually damaging.
The core difference
Not variants of one word. Close to opposites.
- prescribe — order, recommend, lay down: the standard prescribes an annual audit.
- proscribe — prohibit, outlaw: the organisation was proscribed.
Why the error is serious
Writing that a rule "proscribes" a practice when it prescribes one reverses the instruction entirely. In legal, medical or regulatory writing the reader may act on it, which is why this pair appears in every usage guide despite being a single-letter difference.
The roots
Both from Latin scribere, to write. Pre- is before — written in advance as a rule. Pro- here carries the sense of publishing a name publicly, which in Roman practice meant declaring someone outlawed. That is where the prohibition sense comes from.
Frequently asked questions
Which word means forbid?
Proscribe. Prescribe means to order or recommend.
Why is confusing them worse than most mix-ups?
Because they are near-opposites, so the sentence reverses its instruction rather than merely reading oddly.
How do I remember which is which?
A prescription tells you what to do. Proscribed organisations are banned ones.