Many visitors from English speaking countries are surprised by the lack of references to the “Nazis", the “Nazi" party, the “Nazi" regime etc. in Berlin. Plaques, museums and audio guides typically talk about the “National Socialists", and we are often asked if Germany is trying to avoid the proper term.
Actually, National Socialism is the proper term - the word “Nazi" is (and was back then) just German slang, an abbreviation, basically like “dems" as short for “democrats". In the early 20th century such abbreviations were very common: Social Democrats, for example, were (and still are) often referred to as “Sozis", so National Socialists were similarly nicknamed “Nazis". It is considered a proper term only in foreign languages, where there's little or no awareness of its very colloquial nature in German. But German texts, specifically in an official or educational context, typically refrain from slang. After all, the “Nazi" party was actually the National Socialist German Workers' Party. Its ideology was therefore not “Nazism", but National Socialism.
The question about the national/conservative vs. socialist/revolutionary elements in National Socialism has been debated for many decades. The bottom line is that National Socialism was a unique mixture of many ideas, both right- and left-wing. While its collectivist approach placed individual liberties well below the imaginary “common good", it was also very racist - the collective was far more important than the individual, but only because it was the German collective, the so-called “people's community". So instead of calling upon the workers of the world to unite in their common struggle against the upper classes, as Karl Marx put it in the Communist Manifesto of 1848, Adolf Hitler wanted all German classes to unite in their common struggle against the Jews and, well, everybody else. Germany’s pretty rigid rent control as well as its socialized medicine for the elderly, for example, have their roots in the social legislation of the Nazis, whose revolution, however, was never about helping the non-German working class. In other words, their Socialism was meant, to begin with, just for their own German/“Aryan" nation - hence National Socialism.
This toxic mixture of both left- and right-wing elements is understandably confusing. But National Socialism simply didn't last long enough to become anything more than an awfully bad salad of older ideas with no original thought. Even the “Jewish question", as central as it was for the Nazi regime, was not a Nazi term at all, but a much older (19th century) issue. In fact, the “Jewish question" had been debated and addressed for decades by many political parties, both left- and right-wing, before the Nazis came about. Antisemitism was common across the whole political spectrum long before Hitler, who was a very vicious man, but definitely not an original thinker. Marx, although born Jewish, wrote about his own solution to the “Jewish question" as early as 1843, whereas Hitler was only born half a century later, in 1889.
After the Second World War, speaking about “National Socialism" was a big no-no for almost five decades in the GDR (German Democratic Republic), i.e. in East-Germany. The dictatorships of the Soviet bloc wished to avoid any similarity to their own Socialism, so the proper term had to be avoided at all costs. Instead of speaking about National Socialism, they resorted to euphemisms such as Fascism (actually an Italian phenomenon), Hitlerism (as if he created a completely new philosophy) and also Nazism - even though “Nazi" is just slang, “Nazism" was an easy way to avoid the proper term.
Nowadays, fortunately, we live in a democracy and can “call a spade a spade". That's why museum texts, memorial plaques or audio guides in Berlin will tell you about National Socialism and not about “Nazism". It's not meant to downplay the Nazi era, on the contrary - it's all about calling things by their proper name. Nevertheless, on our tours we usually use the words you're familiar with - “Nazism", “Nazis", “the Nazi era" - because it's very important to us to prevent confusion and to be easily understood by our guests.