Because all of these languages have come from a common ancestor, they are called cognate languages, and the similarities between them, which are not confined merely to vocabulary but include elements of grammar as well, might be compared to the physical similarities which between brothers and sisters, or between cousins.
We must remember, however, that the Indo-European is only one of a number of language families throughout the world. Universal agreement has not been reached as to the exact extent of many of these families. The following is a list of some of the more important language families, together with representative languages.