English and German are genetically related. They are both members of the Indo-European family of languages. More specifically, English and German are descended from the West branch of the ancestor language Common Germanic (or Proto-Germanic). This is where the two languages part ways, so to speak, with German representing the High Germanic group and English the Anglo-Frisian branch. The genetic relationship between English and German is made evident by the large number of English-German cognates: e.g. apple vs Apfel, bed vs Bett, house vs Haus, father vs Vater, fish vs Fisch, dream vs Traum— to name but a few.
In addition to words shared through common ancestry, English, being an insatiable word borrower, has incorporated a wealth of German words and phrases into a wide range of semantic fields: e.g. delicatessen (from the German Delikatessen), hamburger (Hamburger), sauerkraut (Sauerkraut), kindergarten (Kindergarten), kaput (kaputt), Pretzel (Brezel), and many many more.
The following list is a sampler of (more or less) commonly used German words and phrases in modern English.
angst (German Angst; literally: anguish): persistent anxiety and fear (hence: angst-ridden)
anschauung (German Anschauung; literally: outlook, view): point of view, attitude (cf. weltanschauung)
autobahn (German Autobahn; literally: motor-road, motorway): freeway, expressway, interstate
Bauhaus (literally: architecture house): A school of design and architecture founded in Weimar by Walter Gropius; relating to the principles of Bauhaus design and aesthetics
bildungsroman (German Bildungsroman; literally: education novel): a coming-of-age novel
blitzkrieg (German Blitzkrieg; literally: “lightning war”): a violent surprise attack by air forces, esp. with reference to the bombing of London in 1940 (also referred to as The Blitz)
ding an sich (German Ding an sich; literally: thing in itself): the perception of things through intuition and thought (as opposed to sensory perception). English philosophers have adopted the literal translation thing-in-itself to describe this school of thought.
dummkopf (German Dummkopf; literally: “dumb-head”): blockhead
echt (German for “real, genuine, true”): used both as an adjective (real) and adverb (really): e.g. cuisine with an echt-Greek flavor; an echt-New Yorker
ersatz (German Ersatz; literally: replacement, substitute): denotes an inferior, second-rate imitation
gestalt (German Gestalt; literally: form, figure, shape): a configuration of phenomena constituting one unique functional unit; Gestalt Psychology is the name of this psychological school of thought.
kaffeeklatsch (German Kaffeeklatsch; literally: “coffee-gossip”): a coffee party (or similar social gathering) with conversation and gossip
katzenjammer (German Katzenjammer; literally: cats’ wailing): loud and confused noise, discordant uproar, caterwaul; hangover (metaphorically)
leitmotiv (leitmotif) (German Leitmotiv; literally: leading motive): guiding theme, recurring musical theme
sturm und drang (German Sturm und Drang; literally: storm and stress): a term of literary criticism used to describe a German literary movement in the late 18th century, characterized by extreme emotionalism; turmoil (metaphorically)
weltanschauung (German Weltanschauung; literally: world view, perception of the world): philosophy of life (cf. anschauung)
wunderkind (German Wunderkind; literally: “miracle-child”): child prodigy
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