Learn Hardcore Portuguese (Portugal): Eu sei disso.

It translates as "I know that" or "I know about that." The sentence indicates that the speaker is aware of or has knowledge of something that has already been mentioned or is understood from context.

How is the word disso formed and what does it mean?

Disso is a contraction of the preposition de (meaning "of" or "about") and the demonstrative pronoun isso (meaning "that"). Together, disso literally means "of that" and refers back to something previously stated or implied.

Why do we use the contraction disso instead of saying de isso?

In Portuguese, it is grammatically correct—and more natural—to contract certain combinations. When de precedes isso, they merge to form disso. This contraction is a standard aspect of Portuguese grammar and helps maintain a fluid, efficient style of expression.

What is the grammatical role of the verb sei in this sentence?

Sei is the first-person singular form of the verb saber in the present tense, meaning "I know." It clearly indicates that the speaker (indicated by eu) currently has the knowledge being discussed.