Dummy pronoun

A dummy pronoun, also called an expletive pronoun or pleonastic pronoun, is a pronoun used to fulfill the syntactical requirements without providing explicit meaning.[entry for "dummy"] As such, it's an example of form-meaning mismatch.
Dummy pronouns are used in many Germanic languages, including German and English. Pronoun-dropping languages such as Spanish, Portuguese, Chinese, and Turkish do not require dummy pronouns.
A dummy pronoun is used when a particular verb argument (or preposition) is nonexistent (it could also be unknown, irrelevant, already understood, or otherwise "not to be spoken of directly") but when a reference to the argument (a pronoun) is nevertheless syntactically required. For example, in the phrase "It is obvious that the violence will continue", "it" is a dummy pronoun, not referring to any agent. Unlike a regular pronoun of English, it cannot be replaced by any noun phrase.
The term "dummy pronoun" refers to the function of a word in a particular sentence, not a property of individual words. For example, "it" in the example from the previous paragraph is a dummy pronoun, but "it" in the sentence "I bought a sandwich and ate it" is a referential pronoun (referring to the sandwich).
Dummy subjects.
Weather "it".
In the phrase "it is raining—", the verb "to rain" is usually considered semantically impersonal, even though it appears as syntactically intransitive; in this view, the required "it" is to be considered a dummy word.
Other views.
However, there have been a few objections to this interpretation. Noam Chomsky has argued that the "it" employed as the subject of English weather verbs ("weather "it"", so called because of its predominant use in reference to weather) can control the subject of an adjunct clause, just like a "normal" subject. For example, compare:
If this analysis is accepted, then the "weather "it"" is to be considered a "quasi-(verb) argument" and not a dummy word.
Some linguists such as D. L. Bolinger go even further, claiming that the "weather "it"" simply refers to a general state of affairs in the context of the utterance. In this case, it would not be a dummy word at all. Possible evidence for this claim includes exchanges such as:
where "it" is implied to mean "the local weather".
Raising verbs.
Other examples of semantically empty "it" are found with raising verbs in "unraised" counterparts. For example:
Extraposition.
Dummy "it" can also be found in extraposition constructions in English, such as the following:
Dummy objects.
In English, dummy object pronouns tend to serve an "ad hoc" function, applying with less regularity than they do as subjects. Dummy objects are sometimes used to transform transitive verbs to transitive light verbs form; "e.g.", "do" → "do it", "to engage in sexual intercourse"; "make" → "make it", "to achieve success"; "get" → "get it", "to comprehend". Prepositional objects are similar; "e.g.", "with it", "up to date"; "out of it", "dazed" or "not thinking". All of these phrases, of course, can also be taken literally. For instance:
Dummy predicates.
It has been proposed that elements like expletive "there" in existential sentences and "pro" in inverse copular sentences play the role of dummy predicate rather than dummy subject, so that the postverbal noun phrase would rather be the embedded subject of the sentence.
Gender.
A dummy pronoun may be conventionally of a particular gender (e.g., "she'll be right, mate" in older Australian vernacular), even though there is no gendered noun with which it must agree.