Formal:
* Desculpe-me: This is the most common and formal way to say "I'm sorry". It's suitable for most situations.
* Peço desculpas: This is a more formal way of saying "I apologize". It's often used in written communication or when addressing someone in a position of authority.
Informal:
* Desculpa: This is a more casual way to say "I'm sorry". It's suitable for friends and family.
* Me desculpa: This is another informal way to say "I'm sorry", slightly more apologetic than "desculpa".
* Sinto muito: This literally translates to "I feel much" and means "I'm very sorry". It's used when you feel very bad about something.
Other options:
* Lamento muito: This means "I lament much" and is a more formal and heartfelt way of saying "I'm very sorry".
* Com licença: This literally means "with permission" and can be used to express a general apology for interrupting someone or causing them inconvenience.
The best choice depends on the specific situation and your relationship with the person you are apologizing to.