Practice is the noun form.
(with -c is the noun)
Practise is the verb form.
(with -s is the verb)
- You need more practice.
(with -c is the noun) - You should practise more.
(with -s is the verb) - It takes a lot of practice to be good at anything.
- You must keep practising to be good at anything.
More examples:
- advice & advise
- device & devise
- licence & license
- prophecy & prophesy