Euphemism is a figure of speech in which a speaker tries to express a meaning felt to be unpleasant as something felt to be more acceptable, because less direct, or less blunt. People in the English-speaking world often avoid saying that someone dear to them has died. Instead, they say "I lost my mother", or "My father passed away last week." The adjective is euphemistic.
The three main areas in which euphemism is common in the UK are death, sex and going to the toilet.
(Toilet itself is a euphemism. It originally meant 'a small cloth used to cover clothes and protect them' [from the French word toile, cloth, + a diminutive suffix]. From its use as 'a cloth over the shoulders during hair-dressing, etc', it seems to have become attached to the articles with which one can make one's toilet (~ get dressed, or made-up - prepared to meet the day), and so 'a place where one could wash'. In due course, this became 'the room in which one could perform those private functions after which one might wash one's hands', or go to the toilet. This now seems the commonest phrase in the UK, although the upper classes still use the word lavatory as an in-group marker, to show their superior education in avoiding the euphemism 'toilet'. Here they show the slippery nature of language. Lavatory is also a euphemism, but rather older. It too means simply 'a place to wash' [from the Latin lavare to wash, + a suffix indicating place]. The preferred euphemism in the US seems to be 'bathroom'.)
Euphemism is a normal way of smoothing social conversation. It can be funny; it can be false and hypocritical. In academic English, it should be avoided. In medical subjects, it would be absurd - and possibly dangerously misleading - to use euphemism, for example in Gynaecology. Although in ordinary life, we may prefer to use a term like 'private parts', a doctor or a nurse may well need to be more precise. In Social Sciences, it would be strange to have to talk about 'departures' instead of 'deaths' when discussing population statistics. People might think one was talking about aeroplane timetables.
On the other hand, beware of dysphemism in academic English. This is the deliberate attempt to make language more direct or shocking. There is a fine line to be drawn between saying something so bluntly that it offends, and wrapping up your meaning so much that it is unclear.
- A note on the etymology may be interesting. The word euphemism comes from Greek and, as a compound of εὖ (eu, ‘well’) and φήμη (phēmē, ‘speech’), means literally ‘good speech’ or ‘speaking well’. However, in ancient Greek the nouns εὐφημία (euphēmia) and εὐφημισμός (euphēmismos), though sometimes used to mean what we understand by euphemism, were originally used to mean the avoidance of words of ill omen during sacrifices to the gods or other religious rituals, and hence, since the surest way of avoiding such ‘unlucky’ speech was to say nothing at all, refraining from speech altogether or complete silence (during religious rituals). (This use of εὐφημία (euphēmia) and εὐφημισμός (euphēmismos) is, or at least comes close to being, an instance of euphemism as we understand the word.)