In some languages, such as English, French, German and Dutch, an impersonal verb always takes an impersonal pronoun (it in English, il in French, es in German, het in Dutch) as its syntactical subject:
In some other languages (necessarily null subject languages and typically pro-drop languages), such as Portuguese, Spanish, Occitan, Catalan, Italian, Romanian, and all the Slavic languages, an impersonal verb takes no subject at all, but it is conjugated in the third-person singular, which is much as though it had a third-person, singular subject:
In the planned auxiliary language Esperanto, where verbs also are not conjugated for person, impersonal verbs are simply stated with no subject given or implied:
Verbs meaning existence may also be impersonal.
An impersonal verb is different from a defective verb in that with an impersonal verb, only one possible syntactical subject is meaningful (either expressed or not), whereas with a defective verb, certain choices of subject might not grammatically possible, because the verb does not have a complete conjugation.
Some linguists consider the impersonal subject of weather verbs to be "dummy pronouns", while others interpret them differently.