Pro-drop language

A pro-drop language (from "pronoun-dropping") is a language in which certain classes of pronouns may be omitted when they are pragmatically or grammatically inferable. The precise conditions vary from language to language, and can be quite intricate. The phenomenon of "pronoun-dropping" is also commonly referred to as zero or null anaphora.[1] In the case of pro-drop languages, null anaphora refers to the fact that the null position has referential properties, meaning it is not a null dummy pronoun. Pro-drop is only licensed in languages that have a positive setting of the pro-drop parameter, which allows the null element to be identified by its governor.[2] In pro-drop languages with a highly inflected verbal morphology, the expression of the subject pronoun is considered unnecessary because the verbal inflection indicates the person and number of the subject, thus the referent of the null subject can be inferred from the grammatical inflection on the verb.[3]

Even though in everyday speech there are instances when who or what is being referred to can be inferred from context, non-pro-drop languages still require the pronoun. However, pro-drop languages allow those referential pronouns to be omitted, or be phonologically null. Among major languages, two which might be called pro-drop languages are Japanese and Korean (featuring pronoun deletion not only for subjects, but for practically all grammatical contexts). Chinese, Slavic languages,[4] American Sign Language and Vietnamese also exhibit frequent pro-drop features. In contrast, non-pro-drop is an areal feature of many northern European languages (see Standard Average European), including French, (standard) German, English[5] and Emilian.[6]

All languages might be considered only partially pro-drop in that they allow deletion of the subject pronoun. These null-subject languages include most Romance languages (French is an exception) as well as all the Balto-Slavic languages and to a limited extent Icelandic. Colloquial and dialectal German, unlike the standard language, are also partially pro-drop; they typically allow deletion of the subject pronoun in main clauses without inversion, but not otherwise. Hungarian allows deletion of both the subject and object pronouns.

History of the term

The term "pro-drop" stems from Noam Chomsky's "Lectures on Government and Binding" from 1981 as a cluster of properties of which "null subject" was one (for the occurrence of pro as a predicate rather than a subject in sentences with the copula see Moro 1997).

Thus, a one-way correlation was suggested between inflectional agreement (AGR) and empty pronouns on the one hand and between no agreement and overt pronouns, on the other. In the classical version, languages which not only lack agreement morphology but also allow extensive dropping of pronouns—such as Japanese, Chinese, Korean, and Vietnamese—are not included, as is made clear in a footnote: "The principle suggested is fairly general, but does not apply to such languages as Japanese in which pronouns can be missing much more freely." (Chomsky 1981:284, fn 47).

The term pro-drop is also used in other frameworks in generative grammar, such as in lexical functional grammar (LFG), but in a more general sense: "Pro-drop is a widespread linguistic phenomenon in which, under certain conditions, a structural NP may be unexpressed, giving rise to a pronominal interpretation." (Bresnan 1982:384).

The empty category assumed (under government and binding theory) to be present in the vacant subject position left by pro-dropping is known as pro, or as "little pro" (to distinguish it from "big PRO", an empty category associated with non-finite verb phrases).[7]

Examples

Japanese

Consider the following examples from Japanese:

このケーキは美味しい。誰が焼いたの？

Kono kēki wa oishii. Dare ga yaita no?

This cake TOPIC tasty-PRESENT. Who SUBJECT bake-PAST EXPLAIN.?

"This cake is tasty. Who baked it?"

知らない。気に入った？

Shiranai. Ki ni itta?

know-NEGATIVE. like-PAST?

"I don't know. Did you like it?"

The words in bold in the English translations (it in the first line; I, you, and it in the second) appear nowhere in the Japanese sentences but are understood from context. If nouns or pronouns were supplied, the resulting sentences would be grammatically correct but sound unnatural. (Learners of Japanese as a second language, especially those whose first language is non-pro-drop like English or French, often supply personal pronouns where they are pragmatically inferable, an example of language transfer.)

Chinese

The above-mentioned examples from Japanese are readily rendered into Chinese:

这块蛋糕很好吃。谁烤的?

Zhè kuài dàngāo hěn hǎochī. Shuí kǎo de?

This piece cake DEGREE tasty. Who bake-MODIFY?

"This cake is tasty. Who baked it?"

不知道。喜欢吗?

Bù zhīdào. Xǐhuan ma?

Not know. like QUESTION-YES/NO?

"I don't know. Do you like it?"

Unlike in Japanese, the inclusion of the dropped pronouns does not make the sentence sound unnatural.

Arabic

Arabic is considered a null-subject language, as demonstrated by the following example:

ساعد غيرك، يساعدك

sāʻid ghayrak, yusāʻiduk.

Help other, help.PST.3SG you.

If you help another, he helps you.

Turkish

Sen-i gör-dü-m

2SG-ACC see-PST-1SG

I saw you.

The subject "I" above is easily inferable as the verb gör-mek "to see" is conjugated in the first person simple past tense form. The object is indicated by the pronoun seni in this case. Strictly speaking, pronominal objects are generally explicitly indicated, although frequently possessive suffixes indicate the equivalent of an object in English, as in the following sentence.

Gel-diğ-im-i gör-dü-n mü?

come-NMLZ-POS.1SG-ACC see-PST-2SG Q

Did you see me coming?

In this sentence, the object of the verb is actually the action of coming performed by the speaker (geldiğimi "my coming"), but the object in the English sentence, "me", is indicated here by the possessive suffix -im "my" on the nominalised verb. Both pronouns can be explicitly indicated in the sentence for purposes of emphasis, as follows:

Sen ben-im gel-diğ-im-i gör-dü-n mü?

2SG 1SG-POSS come-"ing"-POS.1SG-ACC see-PST-2SG Q

Did you see me coming?

Swahili

In Swahili, both subject and object pronouns can be omitted as they are indicated by verbal prefixes.

Ni-ta-ku-saidia.

SUBJ.1SG-FUT-OBJ.2SG-help

I will help you.

English

English is not a pro-drop language. Nonetheless, subject pronouns are almost always dropped in imperative sentences (e.g., Come here), with the subject "you" understood.[8]

In informal speech, the pronominal subject is sometimes dropped. This ellipsis has been called "conversational deletion" and "left-edge deletion",[9][10][11] and is common in informal spoken English as well as certain registers of written English, notably diaries.[12] Most commonly, it is the first person singular subject which is dropped.[13]

Some other words, especially copulas and auxiliaries, can also be dropped.

• [Have you] ever been there?
• [I'm] going to the shops. [Do you] want to come?
• [I] haven't been there yet. [I'm] going later.
• Seen on signs: [I am/We are] out to lunch; [I/we will be] back at 1:00 [P.M].
• What do you think [of it]? – I like [it]! (the latter only in some dialects and registers)
• [Do you] want a piece of cake?

In speech, when pronouns are not dropped, they are more often reduced than other words in an utterance.

Relative pronouns, provided they are not the subject, are often dropped in short restrictive clauses: That's the man [whom] I saw.

The dropping of pronouns is generally restricted to very informal speech and certain fixed expressions, and the rules for their use are complex and vary among dialects and registers. A noted instance was the "lived the dream" section of George H. W. Bush's speech at the 1988 Republican National Convention.[14][15][16][17]

Null-subject languages

Main article: Null-subject language

Modern Greek

Subject pronouns are usually omitted in modern Greek. Example:

Βλέπεις εκείνο το κούτσουρο; Θα ήταν καλό για τη φωτιά. Είναι τελείως ξερό.

See that the log? Would be good for the fire. Is completely dried (literal, direct translation)

(Do) you see this log? It would be good for the fire. It has completely dried. (idiomatic translation)

Romance languages

Most Romance languages (with the notable exception of French) are often categorised as pro-drop too, most of them only in the case of subject pronouns. Unlike in Japanese, however, the missing subject pronoun is not inferred strictly from pragmatics, but partially indicated by the morphology of the verb, which inflects for person and number of the subject.

Spanish

In Spanish, the verb is inflected for both person and number, thus expression of the pronoun is unnecessary because it is grammatically redundant.[3] In the following example, the inflection on the verb ver, 'see', signals informal 2nd person singular, thus the pronoun is dropped. Similarly, from both the context and verbal morphology, the listener can infer that the second two utterances are referring to the log, so the speaker omits the pronoun that would appear in English as "it."

¿Ves este tronco? Sería bueno para la fogata. Está completamente seco. (Spanish)

See this log? Would be good for the campfire. Is completely dry (literal, direct translation)

(Do) you see this log? It would be good for the campfire. It is completely dry (English gloss)

Although Spanish is a pro-drop language, not all grammatical contexts allow for a null pronoun. There are some environments that require an overt pronoun. In contrast, there are also grammatical environments that require a null pronoun. According to the Real Academia Española, the expression or elision of the subject pronoun is not random. Rather there are contexts in which an overt pronoun is abnormal, while in other cases the overt pronoun is possible or even required.[18]

The third person pronouns (él, ella, ellos, ellas) in most contexts can only refer to persons. Therefore, when referring to things (that are not people) an explicit pronoun is usually disallowed.[18]

Subject pronouns can be made explicit when used for a contrastive function or when the subject is the focus of the sentence. In the following example, the first person explicit pronoun is used to emphasize the subject.

Yo [y no tú u otra persona] creo que eso estuvo mal.

I [and not you or another person] think that that was wrong.

Subject pronouns can also be made explicit in order to clarify ambiguities that arise due to verb forms that are homophonous in the first person and third person. For example, in the past imperfect, conditional, and the subjunctive, the verb forms are the same for first person singular and third person singular. In these situations, using the explicit pronoun yo (1st person singular) or él, ella (3rd person singular) clarifies who the subject is, since the verbal morphology is ambiguous.[18]

Italian

Vedi questo tronco? Andrebbe bene da bruciare. È completamente secco. (Italian)

See this log? Would go well for burning. Is completely dry (literal, direct translation)

Do you see this log? It would be fit for burning. It is completely dry. (English gloss)

Portuguese

Examples of omitted subject:

Estás a ver este tronco? Seria bom para a fogueira. Secou completamente. (European Portuguese)

Are to see this log? Would be good for the campfire. Dried completely (literal, direct translation)

(Do) you see this log? It would be good for the campfire. It has completely dried. (English gloss)

Está vendo esse tronco? Seria bom pra fogueira. Secou completamente. (Brazilian Portuguese)

Are seeing this log? Would be good for-the campfire. Dried completely (literal, direct translation)

(Do) you see this log? It would be good for the campfire. It has completely dried. (English gloss)

Omission of object pronouns is likewise possible when the referent is clear, especially in colloquial or informal language:

Acho que ele vai rejeitar a proposta, mas pode aceitar.

Think that he goes (to-)reject the proposal, but may accept. (literally)

I think he is going to turn down the proposal, but he may accept it.

Ainda tem macarrão? Não, papai comeu.

Still is there pasta? No, daddy ate. (literally)

Is there pasta left? No, daddy ate it.

The use of the object pronoun in these examples (aceitá-la, comeu-o) would be grammatical but rather unnatural, especially in Brazil.

Ela me procurou ontem e não achou.

She me sought yesterday and not found. (literally)

She looked for me yesterday and didn't find me.

Here não me achou would also be possible.

A: Eu te amo; você também me ama? B: Amo, sim.

A: I you love; you too me love? B: Love-1-SING, yes. (literally)

A: I love you; do you love me too? B: I do.

Omission of the object pronoun is possible even when its referent has not been explicitly mentioned, so long as it can be inferred. The next example might be heard at a store; the referent (a dress) is clear to the interlocutor. In both Brazilian and European Portuguese the pronoun is omitted.

Viu que bonito? Não gosta? Pode comprar? (BP)

Saw how beautiful? Don't like? Can buy? (using polite 2nd person) (BP)

Viste que bonito? Não gostas? Podes comprar? (EP)

Saw how beautiful? Don't like? Can buy? (using informal 2nd person) (EP)

Have you seen how beautiful it is? Do you like it? Can you buy it? (English gloss)

Modern Spanish and Portuguese are also notable amongst Romance languages because they have no specific pronouns for circumstantial complements (arguments denoting circumstance, consequence, place or manner, modifying the verb but not directly involved in the action) or partitives (words or phrases denoting a quantity of something). However, Medieval language had them, e.g. Portuguese hi and ende.

Compare the following examples in which Spanish, Portuguese, Galician, and Romanian have null pronouns for place and partitives, but Catalan, French, Occitan, and Italian have overt pronouns for place and partitive.

Languages in Europe

  Non-pro-drop languages

  Pro-drop being displaced by a non-pro-drop language

Circumstantial complement denoting place

• "I'm going [there]!"
  • Spanish ¡Voy!
  • Portuguese Vou!
  • Galician Vou!
  • Romanian Mă duc!
  • Catalan Hi vaig!
  • French J'y vais !
  • Occitan I vau!
  • Italian Ci vado!

Partitive denoting quantity

• "I have four of them."
  • Spanish Tengo cuatro.
  • Portuguese Tenho quatro.
  • Galician Teño catro.
  • Romanian Am patru.
  • Catalan En tinc quatre.
  • French J'en ai quatre.
  • Occitan N'ai quatre.
  • Italian Ne ho quattro.

Slavic languages

All Slavic languages behave in a similar manner to the Romance pro-drop languages. Example:

Бачу [яго]. Ідзе. Belarusian

Виждам го. Идва. Bulgarian

Vidim ga. Dolazi. Croatian

Vidím ho. Jde. Czech

Го гледам. Доаѓа. Macedonian

Widzę go. Idzie. Polish

Вижу [его]. Идёт. Russian

Видим га. Долази. Serbian

Vidím ho. Ide. Slovak

Vidim ga. Prihaja. Slovene

Бачу [його]. Іде. Ukrainian

"I see him. He is coming."

Here he in the second sentence is inferred from context. In the East Slavic languages even the objective pronoun "его" can be omitted in the present and future tenses (both imperfect and perfective). As with the Romance languages mentioned above, the missing pronoun is not inferred strictly from pragmatics, but partially indicated by the morphology of the verb (Вижу, Виждам, Widzę, Vidim, etc...). However, the past tense of both imperfective and perfective in modern East Slavic languages inflects by gender and number rather than the person due to the fact that the present tense conjugations of the copula "to be" (Russian быть, Ukrainian бути, Belorussian быць) have practically fallen out of use. As such, the pronoun is often included in these tenses, especially in writing.

Finno-Ugric languages

In Finnish, the verb inflection replaces first and second person pronouns in simple sentences, e.g. menen "I go", menette "all of you go". Pronouns are typically left in place only when they need to be inflected, e.g. me "we", meiltä "from us". There are possessive pronouns, but possessive suffixes, e.g. -ni as in kissani "my cat", are also used, as in Kissani söi kalan ("my cat ate a fish"). A peculiarity of colloquial Finnish is that the pronoun me ("we") can be dropped if the verb is placed in the passive voice (e.g. haetaan, standard "it is fetched", colloquial "we fetch"). In the Estonian language, a close relative of Finnish, the tendency is less clear. It generally uses explicit personal pronouns in the literary language, but these are often omitted in colloquial Estonian.

Hungarian is also pro-drop, subject pronouns are used only for emphasis, as example (Én) mentem "I went", and because of the definite conjugation, object pronouns can be often elided as well; for example, the question (Te) láttad a macskát? "Did (you) see the cat?" can be answered with just láttam "(I) saw (it)", because the definite conjugation renders the object pronoun superfluous.

Hebrew

Modern Hebrew, like Biblical Hebrew, is a "moderately" pro-drop language. In general, subject pronouns must be included in the present tense. Since Hebrew has no verb forms expressing the present tense, the present tense is formed using the present participle (somewhat like English I am guarding). The participle in Hebrew, as is the case with other adjectives, declines only in grammatical gender and number (like the past tense in Russian), thus:

I (m.) guard (ani shomer) = אני שומר‎

You (m.) guard (ata shomer) = אתה שומר‎

He guards (hu shomer) = הוא שומר‎

I (f.) guard (ani shomeret) = אני שומרת‎

We (m.) guard (anachnu shomrim) = אנחנו שומרים‎

Since the forms used for the present tense lack the distinction between grammatical persons, explicit pronouns must be added in the majority of cases.

In contrast, the past tense and the future tense the verb form is inflected for person, number, and gender. Therefore, the verb form itself indicates sufficient information about the subject. The subject pronoun is therefore normally dropped, except in third-person.[19]

I (m./f.) guarded (shamarti) = שמרתי‎

You (m. pl.) guarded (sh'martem) = שמרתם‎

I (m./f.) will guard (eshmor) = אשמור‎

You (pl./m.) will guard (tishm'ru) = תשמרו‎

Many nouns can take suffixes to reflect the possessor, in which case the personal pronoun is dropped. In daily modern Hebrew usage, inflection of nouns is common only for simple nouns, and in most cases, inflected possessive pronouns are used. In Hebrew, possessive pronouns are treated mostly like adjectives and follow the nouns which they modify. In biblical Hebrew, inflection of more sophisticated nouns is more common than in modern usage.

Generalizations across languages

Spanish, Italian, Catalan, Occitan and Romanian can elide subject pronouns only (Portuguese sometimes elides object pronouns as well), and they often do so even when the referent has not been mentioned. This is helped by person/number inflection on the verb. It has been observed that pro-drop languages are those with either rich inflection for person and number (Persian, Polish, Portuguese, etc.) or no such inflection at all (Japanese, Chinese, Korean, etc.), but languages that are intermediate (English, French, etc.) are non-pro-drop.

While the mechanism by which overt pronouns are more "useful" in English than in Japanese is obscure, and there are exceptions to this observation, it still seems to have considerable descriptive validity. As Huang puts it, "Pro-drop is licensed to occur either where a language has full agreement, or where a language has no agreement, but not where a language has impoverished partial agreement."[20]

Other language families and linguistic regions

Among the Indo-European and Dravidian languages of India, pro-drop is the general rule though many Dravidian languages do not have overt verbal markers to indicate pronominal subjects. Mongolic languages are similar in this respect to Dravidian languages, and all Paleosiberian languages are rigidly pro-drop.

Outside of northern Europe, most Niger–Congo languages, Khoisan languages of Southern Africa and Austronesian languages of the Western Pacific, pro-drop is the usual pattern in almost all linguistic regions of the world. In many non-pro-drop Niger–Congo or Austronesian languages, like Igbo, Samoan and Fijian, however, subject pronouns do not occur in the same position as a nominal subject and are obligatory, even when the latter is present. In more easterly Austronesian languages, like Rapa Nui and Hawaiian, subject pronouns are often omitted even though no other subject morphemes exist. Pama–Nyungan languages of Australia also typically omit subject pronouns even when there is no explicit expression of the subject.

Many Pama–Nyungan languages, however, have clitics, which often attach to nonverbal hosts to express subjects. The other languages of Northwestern Australia are all pro-drop, for all classes of pronoun. Also, Papuan languages of New Guinea and Nilo-Saharan languages of East Africa are pro-drop.

Among the indigenous languages of the Americas, pro-drop is almost universal, as would be expected from the generally polysynthetic and head-marking character of the languages. That generally allows eliding of all object pronouns as well as subject ones. Indeed, most reports on Native American languages show that even the emphatic use of pronouns is exceptionally rare. Only a few Native American languages, mostly language isolates (Haida, Trumai, Wappo) and the Oto-Manguean family are known for normally using subject pronouns.

Pragmatic inference

Classical Chinese exhibits extensive dropping not only of pronouns but also of any terms (subjects, verbs, objects, etc.) pragmatically inferable, giving a very compact character to the language. Note, however, that Classical Chinese was a written language, and such word dropping is not necessarily representative of the spoken language or even of the same linguistic phenomenon.

See also

• Null-subject language – Language whose grammar permits an independent clause to lack an explicit subject
• Zero copula – Lacking or omission of a "to be" verb, common in some languages and stylistic in others; many languages such as Arabic and Hebrew lack a "to be" verb which is implicit in the subject.

References

1. Welo, Eirik. "Null Anaphora". Encyclopedia of Ancient Greek Language and Linguistics. doi:10.1163/2214-448x_eagll_com_00000254.
2. Bussmann, Hadumod (2006). Routledge Dictionary of Language and Linguistics. doi:10.4324/9780203980057. ISBN 9780203980057.
3. Flores-Ferrán, Nydia (2007-11-01). "A Bend in the Road: Subject Personal Pronoun Expression in Spanish after 30 Years of Sociolinguistic Research". Language and Linguistics Compass. 1 (6): 624–652. doi:10.1111/j.1749-818X.2007.00031.x. ISSN 1749-818X.
4. Kordić, Snježana (2001). Wörter im Grenzbereich von Lexikon und Grammatik im Serbokroatischen [Serbo-Croatian Words on the Border Between Lexicon and Grammar]. Studies in Slavic Linguistics ; 18 (in German). Munich: Lincom Europa. pp. 10–12. ISBN 978-3-89586-954-9. LCCN 2005530313. OCLC 47905097. OL 2863539W. CROSBI 426497. Summary.
5. Martin Haspelmath, The European linguistic area: Standard Average European, in Martin Haspelmath, et al., Language Typology and Language Universals, vol. 2, 2001, pp. 1492-1510
6. Fabio Foresti, Dialetti emiliano-romagnoli, Enciclopedia Treccani
7. R.L. Trask, A Dictionary of Grammatical Terms in Linguistics, Routledge 2013, p. 218.
8. Geoffrey K. Pullum, Rodney Huddleston, A Student's Introduction to English Grammar, 2005, ISBN 1139643800, p. 170
9. Waldman, Katy (May 4, 2016). "Why Do We Delete the Initial Pronoun From Our Sentences? Glad You Asked". Slate.
10. Randolph H. Thrasher, Shouldn't ignore these strings: A study of conversational deletion, PhD dissertation, 1974, University of Michigan, Ann Arbor (not seen)
11. Randolph H. Thrasher, "One way to say more by saying less: A study of so-called subjectless sentences", 1977, Kwansei Gakuin University Monograph Series 11 Tokyo: Eihosha (not seen)
12. Andrew Weir, "Left-edge deletion in English and subject omission in diaries", English Language & Linguistics 16:1:105-129 (March 2012) doi:10.1017/S136067431100030X
13. Susanne Wagner, "Never saw one – first-person null subjects in spoken English", English Language and Linguistics 22:1:1-34 (March 2018)
14. Bush, George H. W. (18 August 1988). "Address Accepting the Presidential Nomination at the Republican National Convention in New Orleans". American Presidency Project. University of California, Santa Barbara. Retrieved 22 July 2015. Those were exciting days. Lived in a little shotgun house, one room for the three of us. Worked in the oil business, started my own. In time we had six children. Moved from the shotgun to a duplex apartment to a house. Lived the dream - high school football on Friday night, Little League, neighborhood barbecue.
15. Didion, Joan (27 October 1988). "Insider Baseball". The New York Review of Books. Retrieved 22 July 2015. as Bush, or Peggy Noonan, had put it in the celebrated no-subject-pronoun cadences of the "lived the dream" acceptance speech.
16. Greenfield, Jeff (September 2008). "Accepting the Inevitable: What McCain can learn from the acceptance speeches of Reagan, Bush, and Gore". Slate: 2. Note how, as he tells his story, the pronouns drop out, underscoring the idea that this was more a conversation than a speech
17. Winant, Gabriel (21 December 2006). "When the Going Gets Tough". Leland Quarterly. Retrieved 23 July 2015. Bush projects an image as a forthright Westerner who has no truck with fancy language or personal pronouns.
18. "Pronombre Personales Tónicos". Diccionario Panhispánico de Dudas. Real Academia Española. 2005.
19. Hacohen, Gonen; Schegloff, Emanuel A. (2006-08-01). "On the preference for minimization in referring to persons: Evidence from Hebrew conversation". Journal of Pragmatics. Focus-on Issue: Discourse and Conversation. 38 (8): 1305–1312. doi:10.1016/j.pragma.2006.04.004.
20. Huang, C.-T. James. "On the distribution and reference of empty pronouns". Linguistic Inquiry 15: 531-574. 1984.

Further reading

• Bresnan, Joan (ed.) (1982) The Mental Representation of Grammatical Relations, MIT Press, Cambridge, Massachusetts.
• Chomsky, Noam (1981) Lectures on Government and Binding: The Pisa Lectures. Holland: Foris Publications. Reprint. 7th Edition. Berlin and New York: Mouton de Gruyter, 1993.
• Graffi, Giorgio (2001) 200 Years of Syntax. A critical survey, John Benjamins, Amsterdam, The Netherlands.
• Moro, Andrea (1997) The raising of predicates. Predicative noun phrases and the theory of clause structure, Cambridge Studies in Linguistics, Cambridge University Press, Cambridge, England.
• Rizzi, Luigi (1982) Issues in Italian Syntax, Foris, Dordrecht.
• Krivochen, Diego and Peter Kosta (2013) Eliminating Empty Categories. Frankfurt am Main: Peter Lang.
• Jaeggli, Osvaldo, and Ken Safir (1989) The Null Subject Parameter. Dordrecht: Kluwer.

External links

• List of languages including pro-drop (PD) or non-pro-drop (NPD) status.