Polish (język polski, polszczyzna) is the official language of Poland. Polish is the main representative of the Lechitic branch of the Western Slavic languages. It originated in the areas of present-day Poland from several local Western Slavic dialects, most notably those spoken in Greater Poland and Lesser Poland.

Polish was once a lingua franca in various regions of Central and Eastern Europe, mostly due to the political, cultural, scientific and military influence of the Polish-Lithuanian Commonwealth. Although no longer having as great an influence outside of Poland, due in part to the dominance of the Russian language, it is still sometimes spoken or at least understood in western border areas of Ukraine, Belarus and Lithuania as a second language. It shares some vocabulary with the languages of the neighboring Slavic nations, most notably with Ukrainian, Belarusian, Russian, Czech and Slovakian.

Polish has been influenced by contact with foreign languages (foremost Latin, Czech, French, German, Italian, Old Belarusian, Russian and recently it has been virtually bombarded by English, especially American English language elements).

Many words have been borrowed from the German language, as a result of heavy contact with neighbouring Germany. This process has been going on since medieval times. Examples include: szlachta (from German Adelsgeschlecht, nobility), rachunek (Rechnung, account), ratusz (Rathaus, town hall), burmistrz (Bürgermeister, mayor; used only for mayors of smaller cities), handel (Handel, commerce), kac (Kater, hangover), kartofel (Kartoffel, potato; this word is dialectal: most Poles use ziemniak for potato, but both words are understood anywhere), cukier (Zucker, sugar), kelner (Kellner, waiter) and malarz (Maler, painter; also, the word malować has entered Polish as the verb "to paint"). This is especially true of the regional dialects of Upper Silesia.

There are also several words of French origin in the language, most likely dating from the Napoleon era, such as ekran (from French écran, screen), rekin (requin, shark), meble (meuble, furniture), fotel (fauteuil, armchair), plaża (plage, beach) and koszmar (cauchemar, nightmare). Some place names have also been adapted from French, such as the two Warsaw boroughs of Żoliborz (joli bord=beautiful riverside) and Mokotów (mon coteau=my cottage), as well as the suburb of Żyrardów (from the name Girard, with the Polish suffix -ów attached to form the town's name). Other words are borrowed from other Slavic languages, for example, sejm, hańba and brama from Czech.

When borrowing international words, Polish often changes their spelling. For example, the Latinate suffix that is spelled '-tion' in English, corresponds to -cja. To make the word plural, -cja becomes -cje. Examples of this include inauguracja (inauguration), dewastacja (devastation), konurbacja (conurbation) and konotacje (connotations). Also, the digraph qu becomes kw (kwadrant=quadrant; frekwencja=frequency).

Since 1945, as a result of the mass education and mass migrations that affected several countries (particularly Poland), standard Polish has become far more homogeneous, although regional dialects persist, eapecially in the south in the hilly areas bordering the Czech and Slovak Republics. In the western and northern regions that were largely resettled by Poles from the territories annexed by the Soviet Union, the older generation speaks a dialect of Polish characteristic of the former eastern provinces.

Polish is mainly spoken in Poland. In fact, Poland is one of the most homogenous European countries in terms of its mother tongue, as close to 97% of Polish citizens declare Polish as their mother tongue. After the Second World War the previously Polish territories annexed by the USSR retained a large amount of the Polish population that was unwilling or unable to migrate toward the post-1945 Poland and even today ethnic Poles in Lithuania, Belarus, and Ukraine constitute large minorities. In Lithuania 9 percent of the population declared Polish to be their mother tongue. It is by far the most widely used minority language in the Vilniaus Apskritis (Vilnius region) (26% of the population, according to the 2001 census results), but it is also present in other apskritis. In Ukraine, Polish is most often used in the Lwów and Łuck regions. Western Belarus has an important Polish minority, especially in the Brześć and Grodno regions.

There are also significant numbers of Polish speakers in Australia, Austria, Azerbaijan, Brazil, Canada, Czech Republic, Estonia, Finland, Germany, Greece, Hungary, Israel, Ireland, Kazakhstan, Latvia, New Zealand, Romania, Russia, Slovakia, UAE, the UK and the United States.