Above is most commonly used as a preposition but it can also function as an adverb and, more rarely, as an adjective. This last use is quite restricted and normally occurs only in the context of an earlier piece of writing or a location higher up a particular page, as in ‘Interviews will be held at the above address’ or ‘The above information is strictly confidential’.
As an adverb, it can be found in examples like ‘Many of the documents mentioned above can be found on the Internet’ and ‘She stared up at the stars above’.
As a preposition, above means either at a higher level than something or directly above it, as in ‘We began to experience breathing problems above 5,000 metres’ and ‘We lived in the room above the shop’. It can be used to mean higher in amount or standard, as in ‘Temperatures were ten degrees above normal' or more than anything else, as in ‘In their society honesty was prized above all other virtues’. Above can also mean louder or higher than another sound, as in ‘He shouted but he couldn’t make himself heard above all the noise’. In the example ‘Jack was cheating? I thought he was above that sort of thing’, it is used to mean that someone is too virtuous or too proud to engage in a particular activity.
Finally, it is also possible to be above oneself, as in ‘Ever since they made her assistant manager, she’s been getting above herself’, meaning that she thinks she is more important than she really is.