The verb “to practise” does not just mean “to train” but also “to do something habitually or frequently”, “to observe or pursue (something such as a religion” or “to work at (a profession)”. The Collins English Dictionary (Millennium Edition) actually gives “he practises medicine” as an example of this last definition.

In British English, the spelling of the verb is always “practise” regardless of which of the above meanings is applied.

practise [prăk'tĭs] (verb) – The doctor plans to practise medicine in Yorkshire.

Actually, this would be practice. A correct sentence would be “I like to practise my piano playing.” But “I am going to piano practice later”. In medicine, he is not practising, I would hope he’d done all of that at school and is now doing it for real!

Who knew it was a competition!

@maeve
I’ve been hanging around forums for too long. When ‘would of’, ‘definately’ and misplaced ‘it’s’ start to look normal, it’s time to worry…

The rule is the same as for practice/practise, device/devise and advice/advice: -ce for the noun and -se for the verb.

It’s relatively easy with device/devise and advice/advice because the different spellings are pronounced differently, however, you can use that to remember the rule if you get confused about licence/license and practice/practise.