Here's a recipe for schizophrenia:  be an Australian author, who for preference writes in UK English, but who is published mostly in the US.  I'm well on the way to becoming a walking encyclopaedia of English dialect differences.  So let me share some of the madness with practise vs practice.

Practice with a C and practise with an S are two different parts of exactly the same word.

Practice is a noun.  In every English speaking country in the world, with one exception, practice is only ever a noun.  In that one other country, practice is also a verb.

Everywhere else, practise is always the verb.  Hence:


The US lost the S word.  So in the US, the doctor practices medicine at his practice.  Which to my eye looks horribly wrong.

Just to make it more fun, practise also used to mean to play a trick on someone.

The English practice originates from the Old French practiser, so that the 's' version is the original, and in medical Latin is spelt with a 'z'.  It also appears in Greek as praktike.  (It's also in Esperanto as praktike!)  Since it's in both Latin and Greek, that makes it a very old Indo-European word.

The Oxford English Dictionary gives practice as interchangeable these days, thanks to the US practice of spelling practise as practice.  (Confused yet?)

I checked Merriam-Webster's, and it says, to my astonishment, that practise remains acceptable usage in some parts of the US.  It doesn't say where, but I guess they mean New England.  It also gives practise as meaning to play a joke, in US usage!