Title: Serbian language
Content:  Serbian (српски / srpski, ) is the standardized variety of the Serbo-Croatian language mainly used by Serbs. It is the official and national language of Serbia, one of the three official languages of Bosnia and Herzegovina and co-official in Montenegro and Kosovo. It is a recognized minority language in Croatia, North Macedonia, Romania, Hungary, Slovakia, and the Czech Republic. Standard Serbian is based on the most widespread dialect of Serbo-Croatian, Shtokavian (more specifically on the dialects of Šumadija-Vojvodina and Eastern Herzegovina ), which is also the basis of standard Croatian, Bosnian, and Montenegrin varieties and therefore the Declaration on the Common Language of Croats, 
Title: Serbs in Slovenia
Content:  Most Serbs in Slovenia use Slovene as their language of communication, since only 4,300 people in Slovenia declared that they use only Serbian language at home, while about 15,000 declared they use both languages at home. However more than 31,000 people declared their mother tongue as Serbian (and another 36,000 as Serbo-Croatian). A mixed Slovenian–Serbian slang, srboslovenščina, became an "unofficial" language in football and construction building, among other traditional domains of post-war immigrants from former Yugoslavia.
Title: Languages of Serbia
Content:  Serbia has only one nationwide official language, which is Serbian. Other languages spoken in Serbia include Hungarian, Romanian, Slovak, Rusyn, Croatian (all of which are official regional languages in the Vojvodina province), Bosnian, Romani, Albanian, Vlach, Bulgarian, Macedonian, Montenegrin, Bunjevac, etc.
Title: Serbs
Content:  Serbs speak Serbian, a member of the South Slavic group of languages, specifically the Southwestern group. Standard Serbian is a standardized variety of Serbo-Croatian, and therefore mutually intelligible with Standard Croatian and Standard Bosnian (see Differences in standard Serbian, Croatian and Bosnian), which are all based on the Shtokavian dialect. Serbian is an official language in Serbia and Bosnia-Herzegovina and is a recognized minority language in Montenegro (although spoken by a plurality of population), Croatia, North Macedonia, Romania, Hungary, Czech Republic and Slovakia. Older forms of literary Serbian are Church Slavonic of the Serbian recension, which is still used for ecclesiastical purposes, and Slavonic-Serbian—a mixture of Serbian, Church Slavonic and Russian used from the mid-18th century to the first decades of the 19th century. Serbian has active digraphia, using both Cyrillic and Latin alphabets. Serbian Cyrillic was 
Title: Culture of Serbia
Content:   Serbs speak the Serbian language, one of the South Slavic group of languages, specifically in the Southwestern Slavic subgroup together with other Serbo-Croatian varieties and Slovenian. It is mutually intelligible with the Croatian and Bosnian languages (see Differences in standard Serbian, Croatian and Bosnian) and most linguists consider it one of the standard varieties of the common Serbo-Croatian language. The Serbian language comprises several dialects, the standard language is based on the Stokavian dialect. It is an official language in Serbia, Bosnia and Herzegovina and Montenegro. In Hungary, Slovakia, Croatia, North Macedonia and Romania, it is a regionally recognised minority language. There are also historical variants of the Serbian language, namely Old Serbian and Slavonic-Serbian, a blend of Church Slavonic, Russian and Serbian.  Serbian is the only European language with active digraphia, using both Cyrillic and Latin alphabets. The Serbian 
Title: List of lingua francas
Content:  Serbo-Croatian is a lingua franca in several of the territories of the former Yugoslavia, Bosnia, Croatia, Montenegro and Serbia. In those four countries, it is the main native language and is also spoken by ethnic minorities. For example, a Hungarian from Vojvodina and an Italian from Istria might use it as a shared second language. Most people in Slovenia and North Macedonia can understand or speak Serbo-Croatian as well. It is a pluricentric language and is commonly referred to as Bosnian, Croatian, Serbian, or Montenegrin depending on the background of the speaker.
Title: Bosnia and Herzegovina–Serbia relations
Content:  Serbs and Bosniaks ethnolinguistically belong to the South Slavic peoples. The majority of population in Serbia and Bosnia and Herzegovina speak Serbo-Croatian. One of its standard varieties, Serbian, is official in both countries. Bosnian and Croatian, the other varieties of Serbo-Croatian official in Bosnia and Herzegovina, are recognized as minority languages of Serbia.
Title: Languages of Serbia
Content:  The Serbian language predominates in most of Serbia. The Bosnian, Croatian and Bunjevac languages, which are, according to census, spoken in some parts of Serbia are virtually identical to Serbian, while many speakers of the Bulgarian language from south-eastern Serbia speak in the Torlakian dialect, which is considered to be one of the transitional dialects between Bulgarian and Serbian languages. The Serbian language spoken in Serbia has several dialects: Šumadija-Vojvodina, Smederevo-Vršac, Kosovo-Resava, Prizren South Morava, Svrljig-Zaplanje, Timok-Lužnica (Torlakian), Eastern Herzegovina, and Zeta-South Sandžak. The Šumadija-Vojvodina and Eastern Herzegovina dialects are the basis for modern standard Serbian. Throughout part of southern Serbia, a dialect by the name of Torlakian is spoken. Although it has no standard form and continues to be spoken without any form of official status, Torlakian may be seen by some as constituting a separate language. It forms a part of the South Slavic dialect continuum, and is transitional between the eastern south Slavic languages (mainly Bulgarian and Macedonian) and the western south Slavic languages (of which Serbian is a part).
Title: Languages of North Macedonia
Content:  Serbian (српски, srpski) is a standardized register of the Serbo-Croatian language spoken by Serbs, mainly in Serbia, Bosnia and Herzegovina, Montenegro, Croatia and North Macedonia. It is official in Serbia and one of the official languages of Bosnia and Herzegovina, and is the principal language of the Serbs. Serbian is mainly spoken in the municipalities of Čučer Sandevo (~20% of the population) and Staro Nagoričane (19%).
Title: Demographics of Serbia
Content:   The official language is Serbian, member of the South Slavic group of languages, and is native to 6,330,919 or 88% of the population. Recognized minority languages are: Hungarian (mother tongue to 243,146 people or 3.4% of population), Slovak, Romanian, Bulgarian, and Rusyn as well as Bosnian and Croatian which are completely mutually intelligible with Serbian. All these languages are in official use in municipalities or cities where more than a 15% of population consists of national minority. In Vojvodina, provincial administration uses, besides Serbian, five other languages (Hungarian, Slovak, Romanian, Croatian, and Rusyn).

Question: what language do serbs speak?
Answer: Serbian language.