How Many Language Families are there in the World?

The question of how many language families there are in the world is addressed here. The reasons for why it has been so difficult to answer this question are explored. The answer arrived at here is 406 independent language families (including language isolates); however, this number is relative, and factors that prevent us from arriving at a definitive number for the world's language families are discussed. A full list of the generally accepted language families is presented, which eliminates from consideration unclassified (unclassifiable) languages, pidgin and creole languages, sign languages, languages of undeciphered writing systems, among other things. A number of theoretical and methodological issues fundamental to historical linguistics are discussed that have impacted interpretations both of how language families are established and of particular languages families, both of which have implications for the ultimate number of language families.