Slang is a particular kind of colloquial language. It refers to words and expressions which are extremely informal. Slang helps to make speech vivid, colourful and interesting but it can easily be used inappropriately. Although slang is mainly used in speech, it is also often found in the popular press.

It can be risky for someone who is not a native speaker to use slang.
Firstly because some slang expressions may cause offence to some sections of the population. For example, most policemen are quite happy to be referred to as coppers but are offended by the term pigs. Similarly, you could probably use the word sozzled (meaning drunk) in front of anyone but using the words, pissed or arseholed, which also mean drunk, could upset some people.
Secondly, slang words date very quickly. Different generations, for instance, have used different slang expressions to say that something was ‘wonderful’.
pre-war: top-hole 1970s: ace, cosmic
1940s: wizard 1980s: brill, wicked
1960s: fab, groovy
It can be possible to work out a native speaker’s age from the expressions which they use, as people tend to stick with the slang expressions of their youth.
To sum up, you may find it interesting to learn about slang and you may come across slang expressions (particularly when you are watching films or reading popular newspapers or novels) but you might be well advised to avoid using slang yourself.

Here are some examples of some slang words and expressions which you may come across. The ones which are most likely to cause offence are underlined.

– Expressions for money: dough, bread, dosh, loot, brass, spondulicks
– Expressions for the police: pigs, fuzz, cop(per)s, bill
– Expressions for drunk: pissed, sozzled, paralytic, legless, arseholed
– Expressions for a stupid person: wally, prat, nerd, jerk, dickhead, plonker, pillock
– Expressions for lavatory: loo, lav, bog, john
– Expressions for drink: booze, plonk (wine), a snifter, a snort
– Drug-related expressions: a fix, dope, grass, high, stoned, snow (heroin)
– Prison-related expressions: nick (prison), nark (informer), screw (warder)

Slang is often used by one particular group and is unintelligible to other people. Here are some examples from American truck-drivers using CB radio to talk to each other.

grandma lane: slow lane five finger discount: stolen goods super cola: beer
doughnuts: tyres anklebiters: children affirmative: yes
motion lotion: fuel eyeballs: headlights