Wikipedia
Magyarization (also Magyarisation, Hungarization, Hungarisation, Hungarianization, Hungarianisation) was an assimilation or acculturation process by which non-Hungarian nationals came to adopt the Hungarian (also called "Magyar") culture and language, either voluntarily or due to social pressure, often in the form of a coercive policy.
In the era of national awakening, the Hungarian intellectuals transposed the concepts of the so-called "Political Nation" and Nation State from the Western European countries (especially the principles of the similarly highly multiethnic 18th century France), which included the idea of linguistic and cultural assimilation of minorities.
The Hungarian Nationalities Law (1868) guaranteed that all citizens of the Kingdom of Hungary (then part of the Austro-Hungarian Empire), whatever their nationality, constituted politically "a single nation, the indivisible, unitary Hungarian nation", and there could be no differentiation between them except in respect of the official usage of the current languages and then only insofar as necessitated by practical considerations. In spite of the law, the use of minority languages was banished almost entirely from administration and even justice. Defiance of, or appeals to, the Nationalities Law met with derision or abuse. The Hungarian language was overrepresented in the primary schools and almost all secondary education was in Hungarian.
During the long nineteenth century, the Hungarian politicians and intellectuals stood firmly on the contemporary liberal conception of nationality question, which based solely on individualism. With the idea of individualism, they tried to reduce the minority question into a simple linguistic rights question, thus they denied the collective nationality rights and any plans for ethnic autonomous territories.
The data from the censuses of the Habsburg Empire and Kingdom of Hungary are unable to provide any reliable historic information about the ethnic background and identity of the inhabitants. It was due to the practices of contemporary pre-WWI official censuses in Europe, which based only on the so-called "first language" principle or "mostly used language" of the person or family on a highly multi-ethnic society and territory as the Habsburg ruled provinces and countries.
More than 1.5 million economic migrants moved to the United States from Kingdom of Hungary between the 1900-1914 period. This mass migration also had huge effect on the ratios of ethnic minorities in Kingdom of Hungary, because more than 2/3 part of these immigrants in the USA belonged to the ethnic minorities.
By the end of the 19th century, the state apparatus was entirely Hungarian in language, as were business and social life above the lowest levels. The Magyarization of the towns had proceeded at an astounding rate. Nearly all middle-class Jews and Germans and many middle-class Slovaks and Ruthenes had been Magyarized. The percentage of the population with Hungarian as its mother tongue grew from 46.6% in 1880 to 54.5% in 1910. The 1910 census (and the earlier censuses) did not register ethnicity, but mother tongue (and religion) instead, based on which it is sometimes subject to criticism. However, most of the Magyarization happened in the centre of Hungary and among the middle classes, who had access to education; and much of it was the direct result of urbanization and industrialization. It had hardly touched the rural populations of the periphery, and linguistic frontiers had not shifted significantly from the line on which they had stabilized a century earlier.
The process continued also in post- Trianon era. The political and cultural rights offered to interwar Hungary's ethnic minorities were more limited than their equivalents in any other country of East-Central Europe. While anyone who resisted Magyarization was, indeed, subject to political and cultural handicaps, he was not subject to the kinds of civic and fiscal tricks (prejudicial court proceedings, overtaxation, biased application of social and economic legislation) that some of Hungary's neighbors often inflicted on their ethnic minorities.