I'm sure that you have a pretty good vocabulary, but do you sometimes use the wrong form of a word when speaking and writing? It's a common problem that can be fixed with careful consideration and practice. Let's get the ball rolling (start) with this exercise.
Task 1: Choose the correct missing form in each sentence
Task 2: Now the hardest part...write your own example sentences with the correct answers.
Link: Learn Word Forms
Link: Vocabulary Exercise - How well can you do?
Link: Noun and Adjective Forms