A municipal district is an administrative entity comprising a clearly-defined territory and its population. It can refer to a city, a town, a village, a small grouping of them, or a rural area.
In Brazil, municipal districts are, in general, subdivisions of a municipality and do not enjoy political autonomy in Brazil. Municipal districts seats are generally located in villages within the geographic area of a municipality, but sometimes can refer to neighbourhoods adjacent to the city that hosts the municipal seat. In big cities such as São Paulo and Rio de Janeiro districts can host a sub-prefecture (or sub-city hall). Municipal districts in Brazil succeed the old Portuguese parishes from the Brazilian colonial administration.
During the 'New State' (Estado Novo), president Getúlio Vargas, published the Decree-law no. 311, of 2 March 1938, which in its article 3, defined that municipalities' seats would have the status of cities and municipal districts would be named upon their districtal seat's name. 
Another type of district is the Federal District, which shares the status of state among the other 26 states. The government of the Federal District has the status of state and municipal government at the same time, with its seat located in Brasília.
In Canada, municipal districts are a type of rural municipality in Alberta that is governed by elected councils with the mandate to administer rural areas that can include farmlands, resource areas, and unincorporated hamlets and rural residential subdivisions.  Statistics Canada recognizes Alberta's 64 municipal districts as a type of census subdivision for statistical purposes. 
In Alberta, the term county is synonymous with the term municipal district and is not its own incorporated municipal status that is different from that of a municipal district. As such, Alberta Municipal Affairs provides municipal districts with the opportunity to brand themselves either as municipal districts or counties in their official names.
A county in Alberta used to be a type of designation in a single-tier municipal system, but it was changed to "municipal district" under the Municipal Government Act, when the County Act was repealed in the mid-1990s. They were then also permitted to retain the usage of county in their official names. 
Statistics Canada also refers to Nova Scotia's 12 district municipalities as municipal districts for census subdivision purposes.  The City of Flin Flon in Manitoba also held a municipal district status between 1933 and 1946. 
In the Dominican Republic, when a municipality consists of more than one urban center, those beside the municipalities seat can be elevated to the status of a municipal district (distrito municipal). A municipal council (Junta Municipal) for such a municipal district is nominated by the municipal council of the municipality to which it belongs (Ley 3455 Titulo I Capitulo IV). 
In Ireland, each county and city and county is divided into municipal districts consisting of one or more local electoral areas (LEAs). The members elected to the county council or the county and city council for these LEAs are also municipal district members for the relevant areas. Some municipal districts are titled "borough districts" (Clonmel, Drogheda, Sligo and Wexford) or "metropolitan districts" (Limerick and Waterford), though they have no additional powers.   This does not apply to the in the case of the counties of Dún Laoghaire–Rathdown, Fingal or South Dublin, or to the cities of Cork, Dublin or Galway.
The system of municipal districts came into operation from 1 June 2014 following local elections in May, at the same time as the abolition of town and borough councils. 
In Russia, municipal districts are a form of local self-government  and a type of municipal formations. They are usually formed within the borders of existing administrative districts.
In the United States, the District of Columbia is divided into two municipal districts, based on the city's wards, solely for the purposes of electing delegates in the Democratic Party's presidential primaries to the Democratic National Convention.
A county is a geographical region of a country used for administrative or other purposes in certain modern nations. The term is derived from the Old French comté denoting a jurisdiction under the sovereignty of a count (earl) or a viscount. Literal equivalents in other languages, derived from the equivalent of "count", are now seldom used officially, including comté, contea, contado, comtat, condado, Grafschaft, graafschap, and zhupa in Slavic languages; terms equivalent to English language administrative terms such as municipality, district, circuit and commune/community are now often instead used.
A district is a type of administrative division that, in some countries, is managed by the local government. Across the world, areas known as "districts" vary greatly in size, spanning regions or counties, several municipalities, subdivisions of municipalities, school district, or political district.
Russia is divided into several types and levels of subdivisions.
Flin Flon is a mining city, located on a correction line on the border of the Canadian provinces of Manitoba and Saskatchewan, with the majority of the city located within Manitoba. Residents thus travel southwest into Saskatchewan, and northeast into Manitoba. The city is incorporated in and is jointly administered by both provinces.
An okrug is a type of administrative division in some Slavic states. The word "okrug" is a loanword in English, alternatively translated as "area", "district", or "region".
The Province of Manitoba, similar to other Canadian provinces and territories, is governed through a Westminster-based parliamentary system. The Manitoba government's authority to conduct provincial affairs is derived from the Constitution of Canada, which divides legislative powers among the federal parliament and the provincial legislatures. Manitoba operates through three levels of government: the executive, the legislative, and the judiciary. The executive branch—the Executive Council of Manitoba—consists of the Premier, who is the head of government and the President of the Executive Council. The legislative branch—Manitoba Legislature—consists of the Speaker and elected members, who are served by the Clerk, the Officers of the Legislative Assembly, and the employees of the legislative service. The Legislative Assembly consists of the 57 members (MLAs) elected to represent the people of Manitoba.
The municipal divisions in Russia, also called municipal formations, are territorial divisions of the Russian Federation which are formally granted the authority to manage local affairs through local self-government. As of January 1, 2020, there are 20,846 municipal divisions in Russia, including 1,673 municipal districts, 635 urban okrugs, and 33 municipal okrugs.
Canada has a total of 3,573 municipalities among its 10 provinces and 3 territories that are subject to some form of local government.