Tools of Characterization
Speech and Language
Contrary to what you will recall after reading the book, both nadsat and formal (or "gentlemanly") English are spoken in A Clockwork Orange; either can be used to characterize the speaker. For starters, nadsat is a special slang developed and used by the "modern youth," or the teens (1.3.3). The formal English, or "gentlemanly goloss," is spoken by the adults, and is particularly "formal" sounding when the authorities (Minister of the Interior, prison chaplain, and doctors) speak it. Thus, the spoken language generally divides opposing types of characters: the young and the old, the violent and the peaceful, the helpless children and the oppressive authorities. Notably, Alex is versed in both dialects, switching between them throughout the book. This signifies that he belongs to both worlds – or, at least, that he is capable of transitioning (eventually) to the adult world.
Although both youth and adults can dress in the "heighth of fashion" within their respective niches of society, Burgess uses clothing as a characterization tool. The nadsat teens dress in a combination of weird gaudiness, Gothicism, and gender-neutrality that makes them easily identifiable. The adults seem to dress like Communists – drab and gray, with no personality. The authority figures, on the other hand, don spiffy suits, much like modern businessmen; their clothing betrays just how important they are. Lastly, the doctors and scientists are also easily identifiable in their "white coats." In fact, in part two of the book, Alex specifically refers to the authorities exclusively as the "important suits" and the scientists as "white-coats."
Music (Knowledge v. Ignorance of)
There are those who know their stuff when it comes to music (that would be Alex, the prison chaplain, and Andy, the record store guy), and there are those who are completely ignorant of it (that would be Dim and Dr. Brodsky). Because of their expertise in and enjoyment of music, we are supposed to like and think highly of Alex, the prison chaplain, and Andy. Due to their ignorance of classical music, Dim and Dr. Brodsky are intended to be soulless and even "fatally flawed" people. For Dim, the problem is his dimness; for Dr. Brodsky, it's his lack of respect for free will and humanity.
Choice of Drink
Ayn Rand has been quoted as saying (in Atlas Shrugged), "Tell me what a man finds sexually attractive and I will tell you his entire philosophy of life." Well, for our purposes here, substitute "sexually attractive" with "choice of alcoholic beverage." Who would have known that what you choose to poison your body with is tell-tale for who or what you are? Listen up, Shmoopers. The nadsat-speaking teenagers all drink milk, a beverage for infants. Alright, so it's milk-plus hallucinogens, but nonetheless, the key substance is milk. The adults (Alex's parents, the alibi "babooschkas" at the bar, and the prison chaplain) prefer Scotch, apparently. So right off the bat we have an interesting dichotomy – a fine alcoholic line.