Moin is a Frisian-language greeting from East Frisia, the eastern Netherlands, North Frisia and Flensburg, meaning hello. Its use spread during the first half of the 20th century over the whole of northern Schleswig-Holstein; it is also used in the Danish dialect Southern Jutish. Due to the German comic character Werner (who always greets with moin), since the 1980s it is used more and more in central Europe as well. Frisian is a Germanic group of closely related languages, spoken by about half a million members of an ethnic group living on the southern fringes of the North Sea in the Netherlands and Germany. ... The landscape to the north of Greetsiel, in East Frisia. ... Nordfriesland (literally Northern Frisia) is a district in Schleswig-Holstein, Germany. ... Flensburg (Danish: Flensborg, Low German: Flensborg, North Frisian: Flansborj) is an independent town in the North of the German state Schleswig-Holstein. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the... Schleswig-Holstein is the northernmost of the 16 Bundesländer in Germany. ... Jutlandic or Jutish (jy(d)sk in Danish), is a term for the dialects of Danish spoken on the peninsula of Jutland. ... Werner is a fictional character, appearing in a number of German comic books and animated films. ... The 1980s decade refers to the years from 1980 to 1989, inclusive, informally sometimes including the years 1979, 1990 and 1991. ...

The word derives from the Frisian word mooi, meaning "beautiful" or "good". In the also popular form Moin Moin, the second moin (also morn) means "day" in Frisian. Similar forms in Low saxon are mooien Dag, mooien Abend, mooien Mor(g)en. Moin is semantically equivalent to the low saxon greeting Tag and replaced it in many areas. Therefore, Moin can be used 24 hours a day. The duplication Moin Moin is used as emphasis and for a more polite form as well. In Southern Jutish, Mojn is used for hello and good bye, but Mojn Mojn is solely used for good bye. Moin moin literally means "(Have a) good day".

People in more southern parts of Germany often mistakenly assume that Moin is a short form of Morgen (meaning "morning") and should be used like "good morning". Saying "Moin moin" in parts of Germany other than the north will brand you as a northerner.

Moin is also a likely root for the Finnish informal greetings moi ("hello" or "hi") and moi moi ("goodbye") which are typical of Southwestern Finnish.