A brief way of writing a word or a phrase that could also be written out in full, using only the letters of the alphabet and possibly full stops. We usually write abbreviations without full stops in British English. Full stops are normal in American English.
Examples are Dr (US Dr.) for Doctor, Prof (US Prof.) for Professor and Capt (US Capt.) for Captain.
An abbreviation does not normally have a distinct pronunciation of its own: we pronounce Dr as ‘Doctor’ and e.g. as ‘for example’.
Some abbreviations are made from the first letters of several words.
The BBC = the British Broadcasting Corporation
UNESCO = United Nations Educational, Scientific and Cultural Organisation
Some initial-letter abbreviations are pronounced letter by letter (e.g. the BBC). Others are pronounced like words (e.g. UNICEF) – these are often called acronyms.
A character which conventionally represents a word or a phrase without using the letters of the alphabet. Familiar examples are 1 for one, $ for dollar and @ for at.
In a purely logographic writing system, such as that of the Chinese, all words are written with logograms. In the alphabetic English writing system, we don’t require any logograms at all. But people prefer to use them, as they are a brief way of writing things that are very frequent or rather long.