Linguistic typology

Linguistic typology is a subfield of linguistics that studies and classifies languages according to their structural features. Its aim is to describe and explain the structural diversity of the world's languages. It includes three subdisciplines: Qualitative typology deals with the issue of comparing languages and within-language variance, Quantitative typology deals with the distribution of structural patterns in the world’s languages, and Theoretical typology explains these distributions.

Qualitative typology
Qualitative typology develops cross-linguistically viable notions or types which provide a framework for the description and comparison of individual languages. A few examples are given below.

Subject-Verb-Object positioning
One set of types is determined by the basic order of subject, verb, and direct object in sentences: These are usually abbreviated SVO and so forth, and may be called "typologies" of the languages to which they apply.
 * Subject Verb Object
 * Subject Object Verb
 * Verb Subject Object
 * Verb Object Subject
 * Object Subject Verb
 * Object Verb Subject

Some languages split verbs into an auxiliary and an infinitive or participle, and put the subject or object between them. For instance, German ("Im Wald habe ich einen Fuchs gesehen" - *"In-the wood have I a fox seen"), Dutch ("Hans vermoedde dat Jan Piet Marie zag leren zwemmen" - *"Hans suspected that Jan Piet Marie saw teach swim") and Welsh ("Mae ' r gwirio sillafu wedi'i gwblhau" - *"Is the check spelling after to complete"). In this case, typology is based on the non-analytic tenses (i.e. those sentences in which the verb is not split) or the position of the auxiliary. German is thus SVO/VSO (without "im Wald" the agent would go first) in main clauses and Welsh is VAP (and P would go after the infinitive).

Both German and Dutch are often classified as V2 languages, as the verb invariantly occurs as the second element of a full clause.

Some languages allow a relatively free constituent order what poses a problem for their classification. To define the basic constituent order type in this case one has to look at frequency of different types in declarative affirmative main clauses in pragmatically neutral contexts, preferably with only old referents. Thus, for instance, Russian is an SVO language, as this is the most frequent constituent order under these conditions, though all sorts of variations are possible and occur in texts. When there is no clear preference under the described conditions the language belongs to the languages with flexible constituent order (a type on its own).

Ergative-accusative
Another common classification is according to whether a language is accusative or ergative. In a language with cases, the classification depends on whether the subject of an intransitive verb has the same case as the agent or the patient of a transitive verb. If a language has no cases, but is AVP or PVA, then a classification may be based on whether the subject of an intransitive verb is on the same side as the agent or the patient of the transitive verb.

Many languages show mixed accusative and ergative behaviour (e.g. ergative morphology marking the verb arguments, on top of an accusative syntax). Other languages (called "active languages") have two types of intransitive verbs&mdash;some of them ("active verbs") join the subject in the same case as the agent of a transitive verb, and the rest ("stative verbs") join the subject in the same case as the patient. Yet other languages behave ergatively only in some contexts (this is called split ergativity, and is usually based on the grammatical person of the arguments or in the tense/aspect of the verb). For example, only some verbs in Georgian behave this way, and, as a rule, only while the tense called aorist is used.

See also: morphosyntactic alignment.

Quantitative typology
Quantitative typology deals with the distribution and co-occurrence of structural patterns in the languages of the world. Two major types of non-chance distribution are preferences (for instance, absolute and implicational universals, semantic maps, hierarchies) and correlations (areal patterns, for instance, Sprachbund).