In the years 1869 – 1950 data for the present population was collected; since 1961, data for the population based on permanent residence was collected.

Sex refers to the biological characteristics of a person, i. e., whether they are anatomically female or male.

Population density represents the number of inhabitants per 1 km².

The number of municipalities has changed over time, mainly due to administrative changes of the number of municipalites by merging, separation or dissolution.

The size group of a municipality is determined according to the number of population (e. g., municipality belongs to the size group 0 – 499 inhabitants because it has 64 inhabitants).

Due to the comparability of time series categories, the ranges of the size group of municipalities (0 – 199 and 200 – 499, 50,000 – 99 999 and 100 000 and more).

The age groups of the population are defined according to their relationship to economic activity.

Age groups are defined by the approximate age limits of the potential beginning and end of economic activity.

Expresses the structure of the population by 5-year age groups.

Marital status expresses the legal status valid in the Slovak Republic related to a marriage (single/married, divorced, widow/widower).

Marital status was collected of the population aged 15 and over.

The highest level of education attained denotes the highest level of education successfully completed. The highest level of education data was collected of the population aged 15 and over.

The group "with basic education" represents the population with completed 1st or 2nd grade of primary school.

The group "with a university degree" represents the population with completed 1st, 2nd or 3rd grade of university.

The group „without school education (15 +)“ represents the population without school education aged 15 and over.

In the years 1950 – 1980, due to the comparability of time series, the category “complete secondary education” includes complete secondary general education and complete secondary vocational education.

Ethnicity was determined in different ways in individual censuses and was characterized differently, therefore the results of individual censuses cannot be transparently compared.

In the years 1921 – 1930, ethnicity was determined by mother tongue. In the post-war censuses before 1991, ethnicity was determined by self-declaration, but the population could only register with one of the officially recognized ethnicities, which did not include, for example, Roma or Jewish ethnicity.

Between the years 1991 - 2011 data on ethnicity was collected self-declaratively, and the population could declare any ethnicity.

In the year 2021 apart from ethnicity, data on another ethnicity was collected, which is not added to the ethnicity structure.

The mother tongue refers to the language that was spoken to a resident most often at home in childhood. The data is self-declaratory.

In the years 1921 – 1980 data on the mother tongue was not collected.

The religious belief is the membership or relationship of a resident to a church, religious society, or religion, or participation in the religious life. The data is self-declaratory.

In the years 1961, 1970, and 1980, data on religious belief was not collected.

Economically active population generally include the sum of all population available for work.

Data on economically active population are not directly comparable in longer time series, due to different methodical approaches in the collection and processing of data.

The population census concept and methodology in the year 2011 and 2021 enabled the quantification of the secondary homeless. The secondary homeless are inhabitants using various types of temporary accommodation and often move between accommodation such as a shelter, a halfway home, an emergency housing facility or stay in unconventional dwelling (recreational facility, emergency facility not intended for housing, mobile house).