A pro-drop language (from "pronoun-dropping") is a language in which certain classes of pronouns may be omitted when they are in some sense pragmatically inferable (the precise conditions vary from language to language, and can be quite intricate). The phenomenon of "pronoun-dropping" is also commonly referred to in linguistics as zero or null anaphora.
In everyday speech there are often instances when who or what is being referred to can be inferred from context. Proponents of the term "pro-drop" take the view that pronouns which in other languages would have those referents can be omitted, or be phonologically null. Among major languages, one which might be called a pro-drop language is Japanese (featuring pronoun deletion not only for subjects, but for practically all grammatical contexts). Chinese, Slavic languages, and American Sign Language also exhibit frequent pro-drop features. Non-pro-drop is rather an areal feature of Standard Average European including French, German, and English.
Some 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, with French being the most notable exception, as well as all the Balto-Slavic languages and to a limited extent Icelandic.
Consider the following examples from Japanese:
- 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?"
- Shiranai. Ki ni itta?
- know-NEGATIVE. like-PAST?
- "I don't know. Do you like it?"
The pronouns 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 unnatural. (Learners of Japanese as a second language, especially those whose first language is non-pro-drop like English or French, often make the mistake of supplying personal pronouns where pragmatically inferable. This is an example of language transfer.)
The above-mentioned examples from Japanese are readily rendered into Chinese:
- Zhè kuài dàngāo hĕn mĕiwèi. Shéi kăo de?
- This piece cake very beautiful taste. Who bake?
- "This cake is very tasty. Who baked it?"
- Bù zhīdào. Xĭhuan ma?
- Not know. like [QUESTION MARKER]?
- "I don't know. Do you like it?"
- Gel-diğ-i-ni gördüm.
- Coming saw.
- I saw you/him/her/it come.
The subject "I" above is easily inferrable as the verb gör-mek is declined in the first person simple past tense form. The object pronoun is supposed to be deduced from the context; where context is not clear enough, it should be supplied. For example, if one wants to make it sure that it was the person spoken to who was seen, one would say:
- Senin geldiğini gördüm.
Arabic language is considered a null subject language. Look at the example:
- ساعد غيرك، يساعدك
- sā‘id ghayraka, yusā‘iduk
- help other, helps you
- You help others, he helps you.
In this example the two pronouns 'you' and 'he' are not realized phonetically, i.e. they are covert; still the meaning is clear.
English is considered a non-pro-drop language. Nonetheless, subject pronouns are almost always dropped in imperative sentences (e.g., Come here). In informal speech, pronouns may sometimes be dropped in other type of sentences, together with some other words, especially copulas and auxiliaries:
- [Have you] ever been there?
- [I'm] going to the shops. [[Do] you] want to come [with [me]]?
- 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)
In speech, when pronouns are not dropped, they are more often elided than other words in an utterance.
Relative pronouns are often dropped in short restrictive clauses: That's the man [whom] I saw.
Note that these elisions are generally restricted to very informal speech and certain fixed expressions, and the rules for their use are complex and vary among dialects.
Null-subject languages 
Modern Greek 
Subject pronouns can be often 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)
Another phenomenon commonly encountered in modern Greek is the omission of the preposition and article in phrases denoting place or movement to place.
- I am at home.
- Είμαι σπίτι.
- I'm going home.
- Πάω σπίτι.
- "I'm going [there]!"
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. Example:
- ¿Ves este tronco? Sería bueno para la fogata. Está completamente seco. (Spanish)
- Seest 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 (idiomatic translation)
- Estás a ver este tronco? Era bom para a fogueira. Secou completamente. (Portuguese)
- Art to see this log ? Was 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. (idiomatic translation)
- Vedi questo tronco? Andrebbe bene da bruciare. È completamente secco. (Italian)
- Seest this log? Would go well for burning. Is utterly dry (literal, direct translation)
- Do you see this log? It would be fit for burning. It is utterly dry. (idiomatic translation)
In Portuguese object pronouns are often omitted. Once more the context helps. Example: Situation: Maria tries on a dress at a store, comes to her husband and asks:
- – Viu que bonito? Não gosta? Pode comprar? (BP) Viste que bonito? Não gostas? Podes comprar? (EP)
- Saw how beautiful? Don't like? Can buy? Polite-2ndPERS-SING PRESENT-INDICATIVE ? (BP)
- Saw how beautiful? Don't like? Can buy? -2ndPERS-SING PRESENT-INDICATIVE ? (EP)
- Have you seen how beautiful it is? Do you like it? Can you buy it?
From the situation, one can understand that she is talking about the dress.
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).[clarification needed] Compare the following:
- "I'm going [there]!"
- "I have four of them."
While French, like English, is a non pro-drop language, pro-drops may occasionally appear in colloquial and so called diary speech. Examples:
- (Je ne) sais pas. – (I) don’t know.
- (Je) t’appellerai demain. – (I) will call you tomorrow.
- (Il ne) comprend rien, machin. – That guy don’t understand a thing.
Also expletive subjects are dropped in French while they are obligatorily expressed in English:
- Je crois __ difficile d'atteindre ce but. FR.
- I find it difficult to reach that goal.
Slavic languages 
All Slavic languages behave in a similar manner to the Romance pro-drop languages. Example:
- Vidim ga. Dolazi. / Видим га. Долази. Serbo-Croatian
- Vidim ga. Prihaja. Slovene
- Виждам го. Идва. Bulgarian
- Widzę go. Idzie Polish
- Vidím ho. Jde. Czech
- Vidím ho. Ide. Slovak
- Вижу [его]. Идёт. Russian
- Бачу [його]. Йде. Ukrainian
- Бачу [яго]. Ідзе. Belarusian
- Го гледам. Доаѓа./ Go gledam. Doagja. Macedonian
- "I see him. He is coming."
Here he in the second sentence is inferred from context. In Russian even the objective pronoun "его" can be omitted in the present and future tenses (both imperfect and perfective). In most Slavic languages (especially the East Slavic ones), this rule is broken in the past tense of both imperfective and perfectve, since the conjugations agree with the gender of the person. 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 (Виждам, Widzę, Vidim, etc...).
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 spoken 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", spoken "we fetch"). In the Estonian language, a close relative of Finnish, the tendency is less clear. It generally uses explicit personal pronouns in written language, but these are often omitted in spoken language.
Hungarian is also pro-drop, subject pronouns are used only for emphasis, as example (Én) megyek "I go", 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.
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 participle lacks the distinction between grammatical persons, pronouns must be added in the majority of cases.
In contrast, the past tense and the future tense are composed of "non-degenerate" conjugations – the verb has a different cross-marked form for each grammatical person, and a properly conjugated verb contains all the information about the subject. The subjective pronoun is therefore normally dropped, except in third-person.
- I (m./f.) guarded (shamarti) = שמרתי
- You (m. pl.) guarded (shamartem) = שמרתם
- I (m./f.) will guard (ehshmor) = 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, etc.), but languages that are intermediate (English, standard French, etc.) are non-pro-drop.
While the mechanism by which overt pronouns are more "useful" in English than in Japanese is obscure, and while 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."
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 or Fijian, however, the 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 non-Pama–Nyungan languages of Northwestern Australia are universally pro-drop for all classes of pronoun. Papuan languages of New Guinea and Nilo-Saharan languages of East Africa are similarly universally pro-drop.
Among Native American languages, pro-drop is almost universal, as would be expected from the generally polysynthetic and head-marking character of the languages. This character generally allows eliding of all object pronouns as well as subject ones: indeed, most reports on Native American languages show even emphatic use of pronouns exceptionally rare. Only a few Native American languages, mostly language isolates (Haida, Trumai) are known to normally use subject pronouns.
Pragmatic inference 
Classical Chinese exhibits extensive dropping not only pronouns, but also 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.
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). According to this parameter, languages like Italian and Spanish may be classified as pro-drop languages, while English and French may not. The exploration of the properties related to the pro-drop was also crucial in identifying the notion of parameter. Empirically, the comparison between English and Italian became very important (cf. Rizzi 1982).
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. It is worth noting that 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). For a general history of this term within the development of syntactic theory, see Graffi 2001.
See also 
- 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 3-89586-954-6. LCCN 2005530313. OCLC 47905097. OL 2863539W. Summary.
- 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
- 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.
- Cook, Manuela, 1997, Uma Teoria de Interpretação das Formas de Tratamento na Língua Portuguesa, Hispania, Vol 80, Nr 3, AATSP, USA
- Graffi, G. (2001) 200 Years of Syntax. A critical survey, John Benjamins, Amsterdam, The Netherlands.
- Moro, A. 1997 The raising of predicates. Predicative noun phrases and the theory of clause structure, Cambridge Studies in Linguistics, Cambridge University Press, Cambridge, England.
- Rizzi, L. (1982) Issues in Italian Syntax, Foris, Dordrecht.
- List of languages including pro-drop (PD) or non-pro-drop (NPD) status.