'Practice' with a 'c' is the noun of the verb 'practise', which is spelt with an 's'. It means to do something more and more in order to improve. For example 'The English practice I had was great' 'I like to practice my English' Exercise, spelt like this, is both a noun and a verb. It's most common meaning is to do some physical activity. For example 'I like to exercise every day' (verb) 'I like to do some exercise every day' (noun) As a verb, it can also have a similar meaning to 'practise', but is not often used like this. For example 'I like to exercise my English' (practise is better) As a noun, it can also mean a piece of work you do (for example, in school) in order to improve/learn something. For example 'This exercise is very difficult!'