Language families, as conceived in the historical study of languages, should not be confused with the quite separate classifications of languages by reference to their sharing certain predominant features of grammatical structure. Such classifications give rise to what are called typological classes.

In fulfilling the requirements of open-ended creativity imposed on language by human beings, grammatical structure has things in common in all known languages, particularly at the deeper levels of grammar. All known languages have words or wordlike elements combined in accordance with rules into sentences; all known languages distinguish in some way nounlike and verblike sentence components; and all known languages have the means of embedding or subordinating one sentence within another as an included clause (e.g., the sun set and we returned home: When the sun set, we returned home; Joan was playing tennis and Joan twisted her ankle: Joan, who was playing tennis, twisted her ankle, or while she was playing tennis, Joan twisted her ankle). Descriptive analyses of all the languages of the world have not yet been prepared, and, of course, there is information about only a minute number of those that are no longer used—namely, those few that were written. But there is enough known to make the assertion of such universal features as have been given with fair confidence. These are often referred to as language universals; their nature and extent is the subject of ongoing discussion and research.

Within these very general guidelines, however, languages exhibit various types of structure. This can most readily be seen by comparing the relations between the forms of words and their syntactic functions in different languages. Such a comparison is the basis of three broad types of language that have been distinguished since the beginning of the 19th century. They are, in fact, more like characteristics than types, in that most languages contain traces of all three, in different proportions.

Classical Chinese made little or no use of word-form variation, such as is found, for example, in Latin, for grammatical purposes. Sentence structure was expressed by word order, word grouping, and the use of specific grammatical words, or particles. Such languages have been called isolating or analytic. Modern Chinese languages are much less analytic than is often believed; probably, Vietnamese is the most fully representative of this type today. Some languages string together, or agglutinate, successive bits, each with a specific grammatical function, into the body of single words. Turkish is a typical agglutinative language: compare Turkish evleri, “houses” (accusative case), in which ev is the root meaning “house,” -ler marks plurality, and -i is the sign for accusative, with Latin domūs, in which -ūs combines the representation of accusative and plural without the possibility of assigning either category separately to one part of the word ending. Latin is in this respect an inflectional, or fusional, language. In a more extreme example, Latin ī “go!” cumulatively represents in one fused form the verb meaning “go,” active voice, imperative mood, second person, and singular number, each a grammatically distinct category.

English, like many other languages, includes features of all three types. In its use of word order alone to distinguish grammatical differences (the dog chased the cat; the cat chased the dog), it resembles Classical Chinese rather than Latin. In a word form such as manliness, in which each bit can be assigned a grammatical function (man the basic noun, -li- the adjective formative, and -ness the abstract noun formative), it makes use of agglutination, whereas plurals such as men and geese and past tenses such as came and ran fuse distinct grammatical categories into a word form in which only arbitrarily can one allot some sound segments, or letters, to one and some to the other.

Assigning languages to different types in this way involves a delicate procedure of balancing one part of the grammar against another and deciding which type of structure predominates and how well the other types are represented. Languages predominantly of each of the types are found in communities at all levels of civilization and with all types of culture.

In the course of transmission, grammatical structures change, just as do pronunciation and meanings, and in time the cumulative effect may be the transference of a language from one overall type to another, although it remains descended from the earlier language and therefore is just as much part of the same historical family. Latin is very different typologically from French in its grammatical structure, but French is nevertheless the form that Latin took in France in the course of time. In the matter of the grammatical relevance of word order, the absence of case inflections in nouns, and the use of verbal auxiliaries instead of single word tense forms, French is more like English, a distant cousin within the Indo-European family, than it is like Latin, its immediate progenitor (compare French j’ai donné, English I have given, Latin dedī). The two sorts of language classification, historical and typological, serve different purposes and are differently based. Language families group languages together on the basis of descent—i.e., unbroken transmission from an earlier common parent language. The evidence is, in the main, systematic correspondences among the shapes of words of similar meanings (e.g., Greek patēr, Latin pater, French père, German Vater, English father). Languages are put into typological classes, with the reservation already mentioned, on the basis of certain overall similarities of structure irrespective of historical relations. Though these two classifications may coincide with some languages, as is the case to a great extent in the Bantu family, they do so only contingently; being based on different data and oriented differently, they do not logically or necessarily imply each other.

In a way, these two systems of classification involve the two most important aspects in which languages must be seen for them to be properly understood: as products of a continuous historical process and also as self-sufficient systems of communication in any one period. Both as a component of cultural history and as a central part of culture itself, language is able to reveal, more than any other human activity and achievement, what is involved in humankind’s distinctive humanity.