German expressions with no comparable English terms

An sich - in itself
Angst – a gloomy, often neurotic feeling of generalized anxiety and depression. Also a feeling of fear, but more deeply and without concrete object. (Many think the meaning is much more specific in English and the German Angst equals "fear". This is not true, as the German Furcht means "fear". The difference is that Furcht is provoked by a specific object or occurrence, while Angst is a more general state of being that does not need to be initiated by anything concrete. It can happen autonomously, i.e. influenced by prior experience of Furcht without reason.)
Ansatz - basic approach
Blitz – sudden overwhelming attack
Blitzkrieg – warfare conducted along these lines
Ding an sich - the thing in itself, from Kant
Doppelgänger - ("double-goer"); a double or look-alike of a person, sometimes the evil twin
Fahrvergnügen - meaning "driving pleasure"
Gemutlicht - cosy
Gesamtkunstwerk - meaning"total work of art" which combines drama, music, and visual arts in equal measure.
Gestalt – Shape, form (Gestalt psychology, a school of German psychology which affirms that all experience consists of gestalten, and that the response of an organism to a situation is a is a complete and unanalyzable whole rather than a sum of the responses to specific elements in the situation)
Gesundheit – “your health” as a toast; an expression of good wishes to someone who has sneezed
Grubelei – grubbing amongst subtleties
Katergefuhl – self-reproachful irritation
Lebensluge – the lie that makes life bearable
Leitmotiv - a musical phrase that associates with a specific person, thing, or idea.
Lied (pronounced "leet") - "song"; specifically in English, "art song"
Lumpen (in lumpenproletariat) – designating persons or groups regarded as belonging to a low or contemptible segment of their class or kind because of their unproductiveness, shiftlessness, alienation, degeneration etc(Proletariat – class of the lowest status in ancient Roman society, ie working class especially the industrial working class)
Realpolitik - (Political science: "real politics"); usually implies the way politics really work, i.e. via the influence of power and money, rather than a political party's given interpretation.
Schadenfreude also Schadensfreude - a malicious satisfaction obtained from the misfortunes of others
Sitz im Leben - Coming to a deeper awareness and understanding of one’s place or situation in life
Sorge - a state of worry, but (like "Angst") in a less concrete, more general sense, worry about the world, one's future, etc.
Sprechgesang - form of musical delivery between speech and singing
Sturm und Drang - "storm and stress" , or confusion (a brief esthetic movement in German literature)
Umwelt – environment.
Wanderlust - the yearning to travel
Weltanschauung - World-view, underlying assumptions about reality. Weltschmerz - World-weariness, senrtimental pessimism and melancholy over the state of the world; despair with the world (often used ironically in German)
Wille zur Macht - a central concept of Nietzsche's philosophy meaning "the Will to Power."
Zeitgeist "spirit of the times"