Worthandworthwhileare adjectives.
Worthis only used after verbs such asbe, seem, look(as a predicative adjective). It means ‘having a particular value’, especially in money:
A:I wonder how much the house isworth?
B:About half a million, probably.
To be worthdoing something is a common expression. It means that something is useful or important enough to do:
A:I haven’t had a reply to my email to Jane.Is it worth phoningher, do you think?(Would it be useful to phone her?)
B:You could try, I suppose.
We decidedit wasn’t worth goingall the way to London to buy books we could get on the Internet.
To be worth itmeans ‘to be of reasonable or good value for the price’:
A business class ticket cost £2,000, butit was worth itfor such a long flight. It was very comfortable.
We useworthwhilebefore a noun (as an attributive adjective) or after verbs such asbe, seem, look(as a predicative adjective). It means ‘useful’, ‘important’ or ‘good enough to be a suitable reward for the money or time spent or the effort made’:
Do you think working in a supermarket is aworthwhilecareer for a highly intelligent person?
We had thought of buying a bigger car, but we didn’t think it wasworthwhile, since there’s just the two of us.