Grammatical Subject
In Spanish we call the grammatical subject in a sentence "el sujeto", i.e the person or thing that performs the action in a sentence. El sujeto can take different forms, a proper noun, a common noun, a pronoun, or even an infinitive acting as a noun. For example:
La niña corre.
The girl runs.
María está hablando por teléfono.
María is talking on the phone.
Nosotros estudiamos español con Kwiziq.
We study Spanish with Kwiziq.
Los perros ladraban mucho.
The dogs were barking a lot.
La mesa es muy grande.
The table is very big.
Fumar perjudica la salud.
Smoking harms health.