Learn Portuguese (Portugal): É importante, mas não o prometo. - It is important, but I do not promise it.

In European Portuguese, short object pronouns like o usually attach to the end of the verb with a hyphen. However, negative words like não act as a magnet, pulling the pronoun to the position before the verb. This rule is why we say não o prometo instead of "não prometo-o".

What exactly does the o mean in this sentence?

Here, o is an object pronoun meaning "it" (referring to the thing being promised). When referring back to a general statement, abstract idea, or an unnamed action like this, Portuguese defaults to the masculine pronoun o.

Where is the word for "I" in não o prometo?

The "I" is built right into the verb. The word prometo is the "I" form of the verb prometer (to promise). Because the verb ending already tells you who is doing the action, Portuguese speakers usually leave out the word eu (I).

Why does the sentence start with just É instead of a word for "It"?

Unlike English, Portuguese does not use a filler word like "it" for general statements or facts. You simply jump straight to the verb. Therefore, just saying É importante covers the entire phrase "It is important".