In linguistic typology, a null-subject language is a language whose grammar permits an independent clause to lack an explicit subject. Such a clause is then said to have a null subject. Typically, null subject languages express person, number, and/or gender agreement with the referent on the verb, rendering a subject noun phrase redundant. In the principles and parameters framework, the null subject is controlled by the pro-drop parameter, which is either on or off for a particular language.
For example, in Italian the subject "she" can be either explicit or implicit:
The subject "she" of the second sentence is only implied in Italian. English and French, on the other hand, require an explicit subject in this sentence.
Of the thousands of languages in the world, a considerable part are null subject languages, from a wide diversity of unrelated language families. They include Albanian, Arabic, Basque, Finnish, Hindi, Hungarian, Italian, Catalan, Chinese, Japanese, Persian, Portuguese (especially European Portuguese[1]), Russian and other Slavic languages, Spanish, Greek, and Tamil, as well as most languages related to these, and many others still.
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In the framework of government and binding theory of syntax, the term null subject refers to an empty category. The empty category in question is thought to behave like an ordinary pronoun with respect to anaphoric reference and other grammatical behavior. Hence it is most commonly referred to as "pro".
This phenomenon is similar, but not identical, to that of pro-drop languages, which may omit pronouns, including subject pronouns, but also object pronouns. While pro-drop languages are null subject languages, not all null subject languages are pro-drop.
In null subject languages that have verb inflection in which the verb inflects for person, the grammatical person of the subject is reflected by the inflection of the verb, and likewise for number and gender.
The following examples come from Portuguese:
As the examples illustrate, in many null subject languages, personal pronouns exist and can be used for emphasis but are dropped whenever they can be inferred from the context. Some sentences do not allow a subject in any form while, in other cases an explicit subject without particular emphasis, would sound awkward or unnatural.
Most Bantu languages are null-subject. For example, in Ganda, 'I'm going home' could be translated as Ŋŋenze ewange or as Nze ŋŋenze ewange, where nze means 'I'.
Latin text: Veni, vidi, vici.
Literal Translation: Came, saw, conquered.
Actual Translation: I came. I saw. I conquered.
Latin text: Cogito ergo sum.
Literal Translation: Think, therefore am.
Actual Translation: I think, therefore I am.
(The above is a rather ambiguous example. In Latin the subject is not necessarily stated through a (personal) noun, but implied through conjugation. Therefore, the subject is present indeed: the first person singular is stated through the “i” in “ven-i“, “vid-i”, “vic-i”, and through the “o” in “cogit-o”. “To think, therefore to be” would be the literal translation of “Cogitare ergo esse“; “I think, therefore I am” is the truly literal translation of “Cogito ergo sum”. The stated examples are hence not a case of null-subject.)
Tamil script: முடிந்துவிட்டது
Transliteration: muṭintuviṭṭatu
Literal Translation: ended
Actual Translation: It has come to an end.
Arabic is considered a null subject language, as demonstrated by the following example:
Arabic text: ساعد غيرك، يساعدك
Transliteration: sā‘id ghayrak, yusā‘iduk
Literal translation: help other, helps you
Idiomatic translation: You help another, he helps you.
Japanese and several other null subject languages are topic-prominent languages; some of these languages require an expressed topic in order for sentences to make sense. In Japanese, for example, it is possible to start a sentence with a topic marked by the particle wa, and in subsequent sentences leave the topic unstated, as it is understood to remain the same, until another one is either explicitly or implicitly introduced. For example, in the second sentence below, the subject ("we") is not expressed again but left implicit:
| Japanese text | した。 | ご |
||||
|---|---|---|---|---|---|---|
| Transliteration | Watashitachi wa | kaimono o | shita. | Ato de | gohan o | tabeta. |
| Literal translation | We (TOPIC) | shopping (OBJ) | did. | After (COMPL) | dinner (OBJ) | ate. |
| Idiomatic translation | "We went shopping. Afterwards, we ate dinner." | |||||
In other cases, the topic can be changed without being explicitly stated, as in the following example, where the topic changes implicitly from "today" to "I".
| Japanese text | ||||||||
|---|---|---|---|---|---|---|---|---|
| Transliteration | Kyō wa | gēmu no | hatsubaibi | na n da | kedo, | kaō ka | dō ka | mayotte iru. |
| Literal translation | Today (TOPIC) | game (GEN) | release date | is | but, | whether to buy | or not | confused. |
| Idiomatic translation | "The game comes out today, but (I) can't decide whether or not to buy (it)." | |||||||
The null subject also occurs in Spanish. Examples:
In Spanish, sentences with a null subject are used more frequently than sentences with a subject. In some cases, it is even necessary to skip the subject to create a grammatically correct sentence.
In some cases (impersonal constructions), a proposition has no referent at all. Pro-drop languages deal naturally with these, whereas many non-pro-drop languages such as English and French have to fill in the syntactic gap by inserting a dummy pronoun. "*Rains" is not a correct sentence; a dummy "it" has to be added: "It rains", French "Il pleut". In most Romance languages, however, "Rains" can be a sentence: Spanish "Llueve", Italian "Piove", Catalan "Plou", Portuguese "Chove", Romanian "Plouǎ", etc. Uralic and Slavic languages also show this trait: Finnish "Sataa", Hungarian "Esik"; Polish "Pada".
There are some languages that are not pro-drop but do not require this syntactic gap to be filled. For example, in Esperanto, "He made the cake" would translate as Li faris la kukon (never *Faris la kukon), but It rained yesterday would be Pluvis hieraŭ (not *Ĝi pluvis hieraŭ).
Research shows that until around 3 years old, children often omit subjects. For Example:
Other languages (sometimes called non-null subject languages) require each sentence to include a subject: this is the case for most Germanic languages, such as English and German, but also in French (unlike most other Romance language), and many others. In some cases, colloquial expressions, particularly in English, less so in German, and occasionally in French, allow for the omission of the subject in the same way that languages such as Spanish and Russian allow using "correct" grammar:
Even in such non-null subject languages as English, it is standard for clauses in the imperative mood to lack explicit subjects; for example:
An explicit declaration of the pronoun in English in the imperative mood is possible, usually for emphasis but not necessary:
French and German offer less flexibility with regards to null subjects. In French, it is neither grammatically correct nor possible to include the subject within the imperative form (the vous in the expression taisez-vous would stem from the fact that se taire, to be silent is a reflexive verb and is thus the object).
In German, the informal form du may be added to the imperative in a colloquial manner for emphasis (Mach du das, you do it). The formal imperative requires the addition of the subject Sie (as in Machen Sie das) because the formal, addressee-specific imperative form of a verb is morphologically identical to the infinitive, which when used by itself belongs in final position and indicates a "neutral" or addressee-nonspecific imperative (e.g., "Bitte nicht stören" ["Please do not disturb"]).
Many international auxiliary languages, while not officially pro-drop, permit pronoun omission with some regularity. In Interlingua, pronoun omission is most common with the pronoun il, which means "it" when referring to part of a sentence or to nothing in particular. Examples of this word include
Il tends to be omitted whenever the contraction "it's" can be used in English. Thus, il may be omitted from the second sentence above: "Es ver que ille arriva deman". In addition, subject pronouns are sometimes omitted when they can be inferred from a previous sentence:
Similarly, Esperanto sometimes exhibits pronoun deletion in casual use. This deletion is normally limited to subject pronouns, especially where the pronoun has been used just previously: