Morphology and Pro Drop

Many, and according to some estimates most, of the world’s languages allow the subject of the sentence to be unexpressed, a phenomenon known as ‘pro(noun) drop’. In a language like Italian, Gianni parla ‘Gianni speaks’ and Parla ‘(S)he speaks’ are both grammatical sentences. This is in contrast to a language like English, in which not expressing the subject leads to an ungrammatical sentence: *Speaks. The difference between being and not being able to leave the subject unexpressed (or, to put it differently, to have a ‘null subject’) has been related to the richness of the verbal paradigm of a language. Whereas Italian has six different agreement endings in the present tense, English only marks the third-person singular differently (with an -s affix, as in John speak-s). Although this correlation with rich agreement is pervasive, it does not successfully capture all the cross-linguistic variation that is attested. Languages like Japanese and Chinese, for instance, allow unexpressed arguments (including subjects) in the absence of any agreement. For these languages, it has been observed that their pronominal paradigms tend to have transparent, agglutinative nominal morphology, expressing case or number features. Trickier perhaps are languages that allow pro drop under certain conditions only. Some languages, such as Finnish or colloquial variants of German, allow it in certain but not all person/number contexts. Other languages, such as Icelandic, allow the subject to be unexpressed only if it is an expletive, the counterpart of English it (cf. It is raining) or there (There is a man in the garden). For these so-called partial pro drop languages, it is still unclear if one can relate their more restricted absence of overt subjects to other observable properties that they possess.