Dummy subject
Does the sentence need a subject word that names nothing?
Meaning
A dummy subject is a word that fills the subject place in a sentence without naming anyone or anything. It lets a language build a full sentence even when there is no participant to name or the main content comes later. Some languages require such a word in weather or existence sentences; others can express these meanings without one. State and existence is about what is being said, not about a word filling the subject place. Words left out but understood covers meaningful words left unsaid; a dummy subject is present but names nothing.
How to spot it
Look for a subject word that does not point to a person or thing. Check whether it fills a required grammatical place rather than referring back to something or pointing to a place.
In your native language
English uses a dummy subject, a subject word that fills a required place but names no person or thing. The word it fills this place in weather and time expressions, and in comments whose main content comes later in the sentence. Unstressed there fills the subject place in sentences that introduce something as present or existing, usually with be. These uses of it and there do not refer back to a thing or point to a place.
It is snowing.
It fills the subject place without naming anything.
It is half past six.
There is a clean towel in the bathroom.
There fills the subject place; in the bathroom gives the location.
It is easy to find this shop.
The words to find this shop tell us what is easy.
It is good that you called.
The words that you called tell us what is good.
In your learning language
Spanish has no required dummy subject, an empty subject word used just to fill a sentence slot. Weather verbs such as llover, existence with hay, and expressions such as es tarde stand without a subject pronoun. Impersonal haber stays singular even before plural nouns, so both hay dos sillas and había dos sillas are standard.
Hoy llueve mucho.
It's raining a lot today.
No empty subject pronoun is needed.
En la cocina hay dos sillas libres.
There are two free chairs in the kitchen.
Hay needs no empty subject and stays in this form before a plural noun.
Es importante descansar.
It's important to rest.
No empty pronoun is needed before es.
Learners whose language requires an empty subject word may add an unnecessary pronoun before llueve or hay. Learners who expect the verb to match a following plural noun may use *habían dos sillas instead of había dos sillas.