Present Tense:
* Formal: É? (Eh?)
* Informal: É? (Eh?) or É isso? (Is that it?)
Past Tense:
* Formal: Foi? (Was it?)
* Informal: Foi? (Was it?) or Foi isso? (Was that it?)
Future Tense:
* Formal: Será? (Will it be?)
* Informal: Será? (Will it be?) or Será isso? (Will that be it?)
Examples:
* Is it hot today?
* Formal: Faz calor hoje? (Fahz ka-loor oi-je?)
* Informal: Tá quente hoje? (Tah kwen-te oi-je?)
* Is it a cat?
* Formal: É um gato? (Eh oom ga-too?)
* Informal: É um gato? (Eh oom ga-too?)
* Is it finished?
* Formal: Está terminado? (Eh-stah ter-mi-na-do?)
* Informal: Tá pronto? (Tah pron-to?)
Important Note: The Portuguese language has a formal and informal register. "É?" is used in both formal and informal settings, while "É isso?" is more informal.
Always consider the context and your relationship with the person you are talking to when choosing the right phrase.