Let me give you an important piece of advice: The key to mastering a language is not about learning individual words - it is about learning COMBINATIONS OF WORDS. In particular, you need to learn which prepositions belong with which phrases involving nouns and adjectives. In this case, we're looking at this combination of words : verb (eg 'be') + defensive + about + object These are all essential elements. You can change the word order of the sentence as dictated by the grammar, but you can't simply omit words. Look at this: He is defensive about [his private life]. = verb + defensive + about + [object] His private life is something which he is defensive about = [object] + verb + defensive + about His private life is something about which he is defensive = about + [object] + verb + defensive I have nothing to be defensive about = subject + verb + [ object including word 'defensive] + about In other words, you always have to have the preposition 'about' to connect the adjective 'defensive' with its object. Whatever the word order, you still have to include 'about'.

..