A loanword (also loan word or loan-word) is a word adopted from one language (the donor language) and incorporated into another language without translation. This is in contrast to cognates, which are words in two or more languages that are similar because they share an etymological origin, and calques, which involve translation.

A loanword is distinguished from a calque (or loan translation), which is a word or phrase whose meaning or idiom is adopted from another language by word-for-word translation into existing words or word-forming roots of the recipient language^[1].

Examples of loanwords in the English language include café (from French café, which literally means "coffee"), bazaar (from Persian bāzār, which means "market"), and kindergarten (from German Kindergarten, which literally means "children's garden").

In a bit of heterological irony, the word calque is an importation from the French noun, derived from the verb calquer (to trace, to copy);^[2] the word loanword is a calque of the German word Lehnwort;^[3] and the phrase "loan translation" is a calque of the German Lehnübersetzung.^[4]

Loans of multi-word phrases, such as the English use of the French term déjà vu, are known as adoptions, adaptations, or lexical borrowings.^[5][6]

Strictly speaking, the term loanword conflicts with the ordinary meaning of loan in that something is taken from the donor language without it being something that is possible to return.^[7]

The terms substrate and superstrate are often used when two languages interact. (However, the meaning of these terms is reasonably well-defined only in second language acquisition or language replacement events, when the native speakers of a certain source language (the substrate) are somehow compelled to abandon it for another target language (the superstrate).^[8]

Most of the technical vocabulary of classical music (such as concerto, allegro, tempo, aria, opera, and soprano) is borrowed from Italian,^[9] and that of ballet from French.^[10]

The studies by Werner Betz (1949, 1939), Einar Haugen (1950, also 1956), and Uriel Weinreich (1953) are regarded as the classical theoretical works on loan influence.^[11] The basic theoretical statements all take Betz's nomenclature as their starting point. Duckworth (1977) enlarges Betz's scheme by the type “partial substitution” and supplements the system with English terms. A schematic illustration of these classifications is given below.^[12]

The expression "foreign word" used in the illustration below is, however, an incorrect translation of the German term Fremdwort, which refers to loanwords whose pronunciation, spelling, and possible inflection or gender have not yet been so much adapted to the new language that they cease to feel foreign. Such a separation of loanwords into two distinct categories is not used by linguists in English in talking about any language. In addition, basing such a separation mainly on spelling as described in the illustration is (or, in fact, was) not usually done except by German linguists and only when talking about German and sometimes other languages that tend to adapt foreign spellings, which is rare in English unless the word has been in wide use for a very long time.

According to the linguist Suzanne Kemmer, the expression "foreign word" can be defined as follows in English: "[W]hen most speakers do not know the word and if they hear it think it is from another language, the word can be called a foreign word.

There are many foreign words and phrases used in English such as bon vivant (French), mutatis mutandis (Latin), and Schadenfreude (German)."^[13] This is however not how the term is (incorrectly) used in this illustration:

On the basis of an importation-substitution distinction, Haugen (1950: 214f.) distinguishes three basic groups of borrowings: “(1) Loanwords show morphemic importation without substitution.... (2) Loanblends show morphemic substitution as well as importation.... (3) Loanshifts show morphemic substitution without importation”. Haugen later refined (1956) his model in a review of Gneuss's (1955) book on Old English loan coinages, whose classification, in turn, is the one by Betz (1949) again.

Weinreich (1953: 47ff.) differentiates between two mechanisms of lexical interference, namely those initiated by simple words and those initiated by compound words and phrases.

Weinreich (1953: 47) defines simple words “from the point of view of the bilinguals who perform the transfer, rather than that of the descriptive linguist. Accordingly, the category ‘simple’ words also includes compounds that are transferred in unanalysed form”. After this general classification, Weinreich then resorts to Betz's (1949) terminology.

Popular loanwords are transmitted orally.

Learned loanwords are first used in written language, often for scholarly, scientific, or literary purposes.^[14]

The English language has borrowed many words from other cultures or languages.

For examples, see Lists of English words by country or language of origin and Anglicization.

Some English loanwords remain relatively faithful to the donor language's phonology even though a particular phoneme might not exist or have contrastive status in English. For example, the Hawaiian word ʻaʻā is used by geologists to specify lava that is relatively thick, chunky, and rough. The Hawaiian spelling indicates the two glottal stops in the word, but the English pronunciation, /ˈɑː(ʔ)ɑː/, contains at most one. In addition, the English spelling usually removes the ʻokina and macron diacritics.^[15]

The majority of English affixes, such as un-, -ing, and -ly, were present in older forms in Old English. However, a few English affixes are borrowed. For example, the English verbal suffix -ize (American English) or ise (British English)* (British English)]]comes from Greek -ιζειν () via Latin* -izare*.

During more than 600 years of the Ottoman Empire, the literary and administrative language of the empire was Turkish, with many Persian, and Arabic loanwords, called Ottoman Turkish, considerably differing from the everyday spoken Turkish of the time. Many such words were exported to other languages of the empire, such as Albanian, Bosnian, Bulgarian, Croatian, Greek, Hungarian, Ladino, Macedonian, Montenegrin and Serbian. After the empire fell after World War I and the Republic of Turkey was founded, the Turkish language underwent an extensive language reform led by the newly founded Turkish Language Association, during which many adopted words were replaced with new formations derived from Turkic roots. That was part of the ongoing cultural reform of the time, in turn a part in the broader framework of Atatürk's Reforms, which also included the introduction of the new Turkish alphabet.

Turkish also has taken many words from French, such as pantolon for trousers (from French pantalon) and komik for funny (from French comique), most of them pronounced very similarly. Word usage in modern Turkey has acquired a political tinge: right-wing publications tend to use more Arabic or Persian originated words, left-wing ones use more adopted from European languages, while centrist ones use more native Turkish root words.^[16]

Almost 350 years of Dutch presence in what is now Indonesia have left significant linguistic traces. Though very few Indonesians have a fluent knowledge of Dutch, the Indonesian language inherited many words from Dutch, both in words for everyday life (e.g., buncis from Dutch boontjes for (green) beans) and as well in administrative, scientific or technological terminology (e.g., kantor from Dutch kantoor for office).^[17] One scholar argues that roughly 20% of Indonesian words can be traced back to Dutch words.^[18]

In the late 17th century, the Dutch Republic had a leading position in shipbuilding. Czar Peter the Great, eager to improve his navy, studied shipbuilding in Zaandam and Amsterdam. Many Dutch naval terms have been incorporated in the Russian vocabulary, such as бра́мсель (brámselʹ) from Dutch bramzeil for the topgallant sail, домкра́т (domkrát) from Dutch dommekracht for jack, and матро́с (matrós) from Dutch matroos

A large percentage of the lexicon of Romance languages, themselves descended from Vulgar Latin, consists of loanwords (later learned or scholarly borrowings) from Latin. These words can be distinguished by lack of typical sound changes and other transformations found in descended words, or by meanings taken directly from Classical or Ecclesiastical Latin that did not evolve or change over time as expected; in addition, there are also semi-learned terms which were adapted partially to the Romance language's character. Latin borrowings can be known by several names in Romance languages: in Spanish, for example, they are usually referred to as "cultismos",^[19][20] and in Italian as "latinismi".

Latin is usually the most common source of loanwords in these languages, such as in Italian, Spanish, French, etc.,^[21][22][23] and in some cases the total number of loans may even outnumber inherited terms^[24][25] (although the learned borrowings are less often used in common speech, with the most common vocabulary being of inherited, orally transmitted origin from Vulgar Latin). This has led to many cases of etymological doublets in these languages.

For most Romance languages, these loans were initiated by scholars, clergy, or other learned people and occurred in Medieval times, peaking in the late Middle Ages and early Renaissance era^[23]- in Italian, the 14th century had the highest number of loans.^[21] In the case of Romanian, the language underwent a "re-Latinization" process later than the others (see Romanian lexis, Romanian language § French, Italian, and English loanwords), in the 18th and 19th centuries, partially using French and Italian words (many of these themselves being earlier borrowings from Latin) as intermediaries,^[26] in an effort to modernize the language, often adding concepts that did not exist until then, or replacing words of other origins. These common borrowings and features also essentially serve to raise mutual intelligibility of the Romance languages, particularly in academic/scholarly, literary, technical, and scientific domains. Many of these same words are also found in English (through its numerous borrowings from Latin and French) and other European languages.

In addition to Latin loanwords, many words of Ancient Greek origin were also borrowed into Romance languages, often in part through scholarly Latin intermediates, and these also often pertained to academic, scientific, literary, and technical topics.

Furthermore, to a lesser extent, Romance languages borrowed from a variety of other languages; in particular English has become an important source in more recent times.

Study of the origin of these words and their function and context within the language can illuminate some important aspects and characteristics of the language, and can reveal insights on the general phenomenon of lexical borrowing in linguistics as a method of enriching a language.^[27]

According to Hans Henrich Hock and Brian Joseph, "languages and dialects... do not exist in a vacuum": there is always linguistic contact between groups.^[28] The contact influences what loanwords are integrated into the lexicon and which certain words are chosen over others.

In some cases, the original meaning shifts considerably through unexpected logical leaps.

The English word Viking became Japanese バイキング (baikingu), meaning "buffet", because the first restaurant in Japan to offer buffet-style meals, inspired by the Nordic smörgåsbord, was opened in 1958 by the Imperial Hotel under the name "Viking".^[29] The German word Kachel, meaning "tile", became the Dutch word kachel meaning "stove", as a shortening of kacheloven, from German Kachelofen, a cocklestove.