The parameter
Every phrase has one element that decides what kind of phrase it is. In the old grey stone bridge that element is bridge: the expression names a bridge, and everything else describes it. That element is the head, and the rest are its dependents. The verb heads a verb phrase in the same way, and the adposition heads an adpositional phrase.
Head directionality asks whether a language puts heads consistently on one side. In a head-initial language the head comes first and its dependents follow: an English preposition precedes its noun phrase, a verb precedes its object. In a head-final language the order is mirrored throughout: Turkish and Japanese use postpositions, place the genitive and the relative clause before the noun, and close the clause with the verb.
The parameter is a strong tendency rather than a law, and it is uneven across the properties it groups. The correlation between object position and adposition type is very close; the correlation with adjective position is not, which is why English can be broadly head-initial and still say grey stone bridge. Dryer recast the classical correlations in terms of branching rather than headedness because the older formulation predicted more consistency than languages show.
How languages vary
- Head-initial: prepositions, postnominal relative clauses, verb before object. Irish, Welsh, Arabic, and broadly English, French, Italian and Spanish.
- Head-final: postpositions, prenominal relative clauses, verb after object. Turkish, Japanese, Korean, Basque, Persian.
- Mixed: consistent on some properties and not others. German and Dutch, with prepositions and postnominal relatives but verb-final subordination; Mandarin, with prenominal modification throughout but the verb before its object.
The distribution is close to even at the level of individual properties and lopsided in how those properties combine. Dryer's WALS chapter 85 counts 577 languages with postpositions against 511 with prepositions out of 1,184. His chapter 95, on the relationship between object position and adposition type, counts 472 object-verb languages with postpositions and 456 verb-object languages with prepositions, against only 14 and 42 in the two mismatched combinations out of 1,142. Adjective order behaves differently: chapter 87 records 879 languages placing the adjective after the noun and 373 before it, which cuts across the grouping rather than reinforcing it.
Consequences for translation
In a head-final language a noun phrase arrives as a queue of modifiers with the noun at the end, so the reader cannot tell what is being described until the queue runs out. In a head-initial language the noun comes first and the modification trails behind. Translating between the two reverses the reading order of the whole phrase rather than of individual words. That reversal is a structure shift at group level, which is what the phrase structure change technique records, and it is compulsory: no ordering of English words puts an eight-word qualifier in front of its head noun and stays readable.
Two consequences are easy to miss. The first concerns terminology. In a head-final language the distinguishing element of a term stands first and the generic head stands last; in a head-initial language it is the reverse. Term lists sorted alphabetically therefore cluster the two languages by different criteria, and a search by head word finds nothing in the head-final list.
The second concerns depth. A head-final language can stack several modifying clauses before a head noun and stay readable, because the reader knows the head is coming. Reproducing that stack after the head produces trailing modification that soon becomes ambiguous about what attaches to what. The usual remedy is to split the phrase into a clause of its own, which is a unit shift and often a transposition as well.
For a reviser, the order of elements inside a noun phrase is not evidence of anything; what matters is attachment.
Examples
TR>EN
- Source: Bakanlık tarafından geçen ay yayımlanan yönetmelik
- Target: the regulation published last month by the ministry
- Comment: Turkish supplies the agent, the time and the participle before the head noun; English gives the head noun first and hangs the same material after it. The elements correspond one to one and their sequence is inverted.
JA>EN
- Source: 姉が作った天ぷら
- Target: the tempura my sister made
- Comment: The Japanese modifying clause precedes its head with no linking word, and the head is the last item in the phrase. English puts the head first, so the order of reading is reversed.
EN>TR
- Source: in accordance with the provisions of the agreement
- Target: anlaşmanın hükümleri uyarınca
- Comment: English opens with a complex preposition and works outward; Turkish closes with a postposition, with the genitive before its head noun. Several English function words correspond to two Turkish suffixes and one postposition, so the reversal comes with a change of rank as well.
References
- Dryer, M. S. (2013). "Order of Adposition and Noun Phrase." In Dryer, M. S. & Haspelmath, M. (eds.), The World Atlas of Language Structures Online, Ch. 85. Leipzig: Max Planck Institute for Evolutionary Anthropology.
- Dryer, M. S. (2013). "Relationship between the Order of Object and Verb and the Order of Adposition and Noun Phrase." WALS Online, Ch. 95.
- Dryer, M. S. (2013). "Order of Adjective and Noun." WALS Online, Ch. 87.
- Dryer, M. S. (1992). "The Greenbergian Word Order Correlations." Language 68, 81–138.
- Croft, W. (2003). Typology and Universals, 2nd edition. Cambridge: Cambridge University Press, Ch. 3.