In
linguistics, a zero or null is a
segment which is not pronounced or written. It is a useful concept in analysis, indicating lack of an element where one might be expected. It is usually written with the symbol "∅", in Unicode U+2205∅EMPTY SET (∅, ∅, ∅, ∅). A common
ad hoc solution is to use the
Scandinavian capital letter Ø instead.
There are several kinds of zero:
In
phonetics and
phonology, a null phoneme or zero phone indicates that no
phone is produced where one might be expected. For example, in
syllable structure analysis,
null onset indicates that a syllable lacks an initial consonant (onset) that is normally required by
phonotactics of the considered language. For an example, see
Standard Chinese phonology#Zero onset.
In
morphology, a
zero morph,[1] consisting of no phonetic form, is an
allomorph of a
morpheme that is otherwise realized in speech. In the phrase two sheep-∅, the plural marker is a zero morph (see
nouns with identical singular and plural forms), which is an allomorph of -s as in two cows. In the phrase I like-∅ it, the verb
conjugation has a zero affix, as opposed to the third-person singular present -s in he likes it.
In
grammar, a zero
pronoun occurs in some languages.[2] In the English sentence nobody knows ∅ the zero pronoun plays the role of the object of the verb, and in ∅ makes no difference it plays the role of the subject. Likewise, the zero pronoun in the book ∅ I am reading plays the role of the relative pronoun that in the book that I am reading. In
generative grammar, this is also referred to as
PRO. In
pronoun-dropping languages, including
null subject languages such as most
Romance languages, the zero pronoun is a prominent feature.
A zero
subordinate conjunction occurs in English in sentences like I know ∅ he likes me, in which the zero conjunction plays the role of the subordinate conjunction that in I know that he likes me.
A zero article is an unrealized
indefinite or
definite article in some languages, such as the plural indefinite article in English.
A
zero copula,[3] in which a
copula such as the verb to be is implied but absent. For example, in
Russian the copula is usually omitted in the
present tense, as in Она красивая (literally: 'She beautiful'). In English the copula is sometimes omitted in some
nonstandard dialects.[4]