Constituent order

In linguistic typology, languages are classified by the constituent order or word order of the subject (or agent), verb, and object (or patient) in a transitive statement. SVO and SOV are most common, followed by VSO, with VOS, OSV, and OVS rare.

In several languages, breaking the verb V into an auxiliary that carries tense and agreement (the "tensed" verb, labeled T) and the non-finite main verb (the "predicate" or "participle", labeled P) can help clarify some ordering phenomena that the SVO system conflates. In sentences with no auxiliary, the main verb occupies T.
 * English is STPO: "Sam has eaten oranges." Questions invert into [W]TSPO, and simple tenses of verbs other than be gain do-support in questions rather than eliding P: "Has Sam eaten oranges?"
 * Modern Romance languages are SoTPO, where pronoun objects (lowercase o) go on the opposite side of the verb compared to noun objects. The TP compound doesn't split as easily as it does in English, and thus questions invert into [W]oTPSO: "Has eaten Sam oranges?"
 * Breton is TSPO in progressive aspect but PTSO in its do-supported simple present: "Is Sam eating oranges" but "Eat does Sam oranges."
 * Biblical Hebrew is traditionally analyzed as VSO. A later analysis proposes that SVO is more common outside narratives, in which a conjunction fuses with the verb and pulls it to the front.
 * Welsh is TSPO: "Has Sam eaten oranges." The standard order for simple tenses in Irish and Welsh is VSO, but do-support has become common in colloquial Welsh. Celtic languages form the participle P by attaching a tense preposition to a gerund (called a verbnoun by Celticists), literally "in eating" or "after eating". Glenda Newton has a theory on how this arose in Old Irish.
 * Yosondúa Mixtec is TPSO: Has eaten Sam oranges. Its strict VSO structure, which keeps even serial verb constructions to the left of the subject and allows only adverbs to precede the verb, is in fact far more common worldwide than the TSPO of Celtic, which appears to derive from SVO.
 * Some languages are topic-prominent in their syntax, distinguishing "given" noun phrases (those providing topic or background information) from "new" noun phrases (those making a comment). Classical Arabic has been described as VGN (verb-given-new), where an object that is given ordinarily precedes the subject. When a subject is both given and "heavy" (long), the sentence tends to flip into SVO, with inna "indeed" often preceding the subject to mark it as a topic.
 * Dutch, German, and Kashmiri are V2 (verb second) in main clauses, where an adverb can push the subject after the finite verb. This results in STOP/AdvTSOP: "Sam has oranges eaten" but "Yesterday has Sam oranges eaten." Rarely the main verb is fronted into PTSO: "Eaten has Sam oranges." "Scrambling" in Wikipedia gives the German example Erwähnt hat er das nicht (lit. "Mentioned has he that not") for "He didn't mention that".
 * Japanese is SOPT: "Sam-ga oranges-o eaten has." So are subordinate clauses in most V2 languages.

In fiction:
 * Yoda's dialect from the Star Wars films is usually POST: "Eaten oranges Sam has." Occasionally it's POTS, especially for a short S: "Eaten oranges has Sam." Without the distinction between tensed and main verbs, it could be analyzed as VOS, OVS, or OSV. Not all Yoda quotes are in this order, as for very important points, Yoda makes an effort to use the STPO order of standard Galactic Basic.
 * Among the languages of Noen, Nognese is TSPO, and Noeneg is even more V2 than German, with auxiliary support in all tenses. One Noeneg-based interlanguage is PTSO, which Noeneg speakers understand as P fronted past T and Nognese speakers understand as T forming the conjugation of P.

Not all 24 orderings of STPO are equally likely in languages. Several tendencies are common, for which linguists have given cognitive functional explanations of varying quality.


 * Subject before object reflects the tendency of subjects to be topics.
 * As the head of the entire sentence, T is commonly found next to one or both of its immediate dependents S and P.
 * P and O are commonly found together, forming a verb phrase (VP), a constituent with P as the head.
 * Orderings with S and O adjacent are more likely to have overt case marking on nouns.
 * A language tends toward one head directionality (either head-dependent or dependent-head) for most constructions.

In an SOV language where the verb agrees with the subject in person and number, the agreement has to jump over the direct object to land at the verb. In addition, the mapping of each noun phrase's grammatical case to its thematic role is not certain until the verb. This can prove challenging for adult L2 learners, encouraging them to switch to SVO, as Latin speakers did when the language gradually became Italian and Old English speakers did under the Norman regime that produced Middle English. The fact that Chinese, English, Spanish, and other SVO languages have over twice as many speakers as SOV languages is evidence for a tendency of widely spoken languages to switch to VO order.

The "brace" orders (TSPO and STOP) reflect a compromise between keeping the verb phrase contiguous and keeping head directionality consistent. When explaining the absence of T?SVO (V in situ whether or not an initial finite auxiliary is present, or SVO/TSPO) and the rarity of brace orders outside Celtic and Germanic, Alexandra Zepter of Rutgers has set forth six violable constraints in an optimality theory that results in a small number of underlying word orders.

There even appears to be a correlation with phonology. Languages with few phonemes show simpler syllable structure (often mostly CV), with less information per syllable. This leads to more agglutinative morphology, more overt case, and somewhat more tendency to remain head-final (SOV). Languages with more phonemes tend toward more consonant clusters and closed syllables. Many phonemes per syllable mean fewer syllables per word, which means it's easier for the next syllable to be an independent word, producing a tendency toward more isolating morphology. This increases homophony and word class (part of speech) ambiguity, which in turn produces more rigid syntax and more opaque idioms and set phrases, and this usually moves the verb before the object (VO) to separate it from the subject.