In linguistics, a false friend is a word in a different language that looks or sounds similar to a word in a given language, but differs significantly in meaning. Examples of false friends include English embarrassed and Spanish embarazada 'pregnant'; English parents versus Portuguese parentes and Italian parenti (both meaning 'relatives'); English demand and French demander 'ask'; and English gift, German Gift 'poison', and Norwegian gift 'married'.
The term was introduced by a French book, Les faux amis: ou, Les trahisons du vocabulaire anglais (False friends, or, the betrayals of English vocabulary), published in 1928.
As well as producing completely false friends, the use of loanwords often results in the use of a word in a restricted context, which may then develop new meanings not found in the original language. For example, angst means 'fear' in a general sense (as well as 'anxiety') in German, but when it was borrowed into English in the context of psychology, its meaning was restricted to a particular type of fear described as "a neurotic feeling of anxiety and depression". Also, gymnasium meant both 'a place of education' and 'a place for exercise' in Latin, but its meaning became restricted to the former in German and to the latter in English, making the expressions into false friends in those languages as well as in Ancient Greek, where it started out as 'a place for naked exercise'.
False friends are bilingual homophones or bilingual homographs, i.e., words in two or more languages that look similar (homographs) or sound similar (homophones), but differ significantly in meaning.
The origin of the term is as a shortened version of the expression "false friend of a translator", the English translation of a French expression (faux amis du traducteur) introduced by Maxime Kœssler and Jules Derocquigny in their 1928 book, with a sequel, Autres Mots anglais perfides.
From the etymological point of view, false friends can be created in several ways.