As they say English is a funny language and we could not agree any less when we come to confusions such as these. You must be wondering what difference a ‘c’ and a ‘s’ can make? Well, if you are a grammar fanatic, the wrong usage here might kill you, as the first one, ‘practice’ is a noun and the other one with the ‘s’ is a verb.
See the following examples:
1) You seem to be out of practise with your guitar.
2) You should practice well.
3) Keep practising this piece till you get it right.
4) I am out of practice.
In the first case, it should be practice.
In the second case it should be practise.
Third and fourth sentences are correct.
To clear the confusion, you need to know the theoretical difference between a Noun and a Verb, as in this case one word is former and other the latter.
Noun: It is that part of speech, which refers to a person, place, and thing and in this case an act in itself (practice). So, going by the definition, practice here is ‘something that is happening’
Verb: it is that part of speech, which indicates action. So, going by the definition, ‘practise’ here is the action by which an act takes place. You can classify the verbs into two categories: transitive and intransitive. But we leave that discussion for another day.
Quick, dirty and effective tip to solve the issue once and for all:
Use these two words to check whether you need to use practice or practise: Use ‘preparation’ (or ‘lessons’) and ‘to prepare’ (in its various forms; e.g., preparing, prepared, prepares).
In case the word that fits in is ‘preparation’ (or ‘lessons’), you need to use ‘practice’ as ‘preparation’ or ‘lessons’ are nouns and a noun can only replace another in a sentence.
In case the sentence makes sense when you use ‘to prepare’ (in its various forms; e.g., preparing, prepared, prepares), you need to use ‘practise’. The reason for this is that ‘to practise’ is a verb, just like ‘to prepare’.
Hope the difference is clear you. Just to add to your learning, you can ‘practise’ with the examples given below:
1) You will need to___________more to win this award.
2) _____of female foeticide is no good for the society.
3) ________will make you perfect.
4) You really need to work hard in order to set up your own lawyer __________.
5) I am ___________ my guitar.
6) She ___________ her instrument on daily basis.
7) I need to ________ my guitar.
8 ) I am a ___________ public speaker.
8 ) Practised
Footnote: PRACTICE IN AMERICA
Whilst many in the US have adopted ‘practise’ as the verb and ‘practice’ as the noun, it is acceptable to use ‘practice’ for both noun and verb in American English.
I must keep practising/practicing that accent.
(both versions acceptable in American English)