The Indo-European languages include some 449 (SIL estimate, 2018 edition) languages spoken by about or more than 3.5 billion people (roughly half of the world population). Most of the major languages belonging to language branches and groups of Europe, and western and southern Asia, belong to the Indo-European language family. Therefore, Indo-European is the biggest language family in the world by number of mother tongue speakers (but not by number of languages in which it is the 3rd or 5th biggest). Eight of the top ten biggest languages, by number of native speakers, are Indo-European. One of these languages, English, is the de facto World Lingua Franca with an estimate of over one billion second language speakers. Each subfamily or linguistic branch in this list contains many subgroups and individual languages. Indo-European language family has 10 known branches or subfamilies, of which eight are living and two are extinct. The relation of Indo-European branches, how they are related to one another and branched from the ancestral proto-language is a matter of further research and not yet well known. There are some individual Indo-European languages that are unclassified within the language family, they are not yet classified in a branch and could be members of their own branch. The 449 Indo-European languages identified in the SIL estimate, 2018 edition, are mostly living languages, however, if all the known extinct Indo-European languages are added, they number more than 800 or close to one thousand. This list includes all known Indo-European languages, living and extinct. A distinction between a language and a dialect is not clear-cut and simple because there is, in many cases, several dialect continuums, transitional dialects and languages and also because there is no consensual standard to what amount of vocabulary, grammar, pronunciation and prosody differences there is a language or there is a dialect. (Mutual intelligibility can be a standard but there are closely related languages that are also mutual intelligible to some degree, even if it is an asymmetric intelligibility.) Because of this, in this list, several dialect groups and some individual dialects of languages are shown (in italics), especially if a language is or was spoken by a large number of people and over a big land area, but also if it has or had divergent dialects. The ancestral population and language, Proto-Indo-Europeans that spoke Proto-Indo-European, estimated to have lived about 4500 BCE (6500 BP), at some