1. A grammatical subject that is not overtly expressed in a sentence but is understood from context or linguistic convention, particularly in pro-drop languages
In Spanish 'Habló' (He/She spoke), the empty subject refers to the understood third-person singular pronoun
Em português 'Falei' (I spoke), o sujeito nulo refere-se ao pronome de primeira pessoa singular entendido
2. In linguistics, a syntactic position for a subject that contains no phonetic material but has semantic and grammatical content
The sentence 'It is raining' contains an expletive empty subject in English
A sentença 'Chove' em português contém um sujeito nulo expletivo