It is used in the following ways:
* In the perfect tenses:
* Present perfect: "He sido feliz" (I have been happy)
* Past perfect: "Había sido difícil" (It had been difficult)
* Future perfect: "Habré sido paciente" (I will have been patient)
* In the passive voice:
* "La casa fue sido construida" (The house was built)
* In certain idiomatic expressions:
* "Ser sido así" (To have been like that)